Steel structure, method for repairing a steel structure, and method for manufacturing a steel structure

Abstract

To shorten the construction period for steel structures. [Solution] The method for repairing steel structures comprises the steps of: preparing the surface of a deteriorated part of a steel structure including steel materials; applying paint to the steel materials to form a coating film; drying the coating film until the tack of the coating film is 2.0 N / φ5 mm or less; and joining a covering sheet to the coating film using the bonding layer contained in the covering sheet.

Description

Technical Field

[0001] The present disclosure relates to a steel structure, a method for repairing a steel structure, and a method for manufacturing a steel structure.

Background Art

[0002] Steel structures such as bridges contain steel materials. Steel materials deteriorate over time due to corrosion. Deteriorated steel materials become defects that can significantly reduce the strength of the steel structure. Therefore, a plurality of coating films for suppressing corrosion are laminated on the steel material (for example, Patent Document 1). Examples of the coating film include a plurality of primer layers containing an epoxy resin, an intermediate coating layer for a fluororesin coating containing an epoxy resin, a top coating layer containing a fluororesin, and the like.

[0003] When repairing or manufacturing a steel structure including a large number of coating films, not only does it take time to form each coating film, but it is also necessary to dry the base layer for a long time before forming each coating film. Therefore, it takes several days to repair or manufacture a steel structure including a plurality of coating films. Moreover, the drying of the base layer needs to be carried out on a day without rain, and it is also necessary to delay the production of the base layer depending on the weather. As a result, the construction period of the steel structure is very long.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] An object of the present disclosure is to shorten the construction period of a steel structure.

Means for Solving the Problems

[0006] A first method for repairing a steel structure according to an embodiment of the present disclosure is A process for preparing the surface of deteriorated parts of steel structures, including steel materials, The process of applying paint to the steel material to form a coating film, A step of drying the coating film until the tack of the coating film becomes 2.0 N / φ5 mm or less, The process includes a step of joining the coating film to the coating sheet using the bonding layer contained in the coating sheet.

[0007] A second method for repairing a steel structure according to one embodiment of the present disclosure is: A process for preparing the surface of deteriorated parts of steel structures, including steel materials, The process of applying paint to the steel material to form a coating film, The process of drying the aforementioned coating for two hours or more, The process includes a step of joining the coating film to the coating sheet using the bonding layer contained in the coating sheet.

[0008] A method for manufacturing a first steel structure according to one embodiment of the present disclosure is: The process of applying paint to steel material to form a coating, A step of drying the coating film until the tack of the coating becomes 2.0 N / φ5 mm or less, The process includes a step of joining the coating sheet to the coating film using the bonding layer contained in the coating sheet.

[0009] A method for manufacturing a second steel structure according to one embodiment of the present disclosure is: The process of applying paint to steel material to form a coating, The process of drying the aforementioned coating for two hours or more, The process includes a step of joining the coating sheet to the coating film using the bonding layer contained in the coating sheet.

[0010] A steel structure according to one embodiment of the present disclosure is Steel materials, The coating film and The covering sheet and the following are included in this order: The ratio of the post - test peel strength of the coating film of the coated sheet after the weather resistance test to the initial peel strength of the coating film of the coated sheet is 70% or more.

Advantages of the Invention

[0011] According to the present disclosure, the construction period of the steel structure can be shortened.

Brief Description of the Drawings

[0012] [Figure 1A] FIG. 1A is a diagram for explaining an embodiment in a single form, and is a cross - sectional view showing an example of a steel structure. [Figure 1B] FIG. 1B is a cross - sectional view showing another example of a steel structure. [Figure 2A] FIG. 2A is a cross - sectional view showing an example of a coated sheet that may be included in the steel structure shown in FIG. 1A. [Figure 2B] FIG. 2B is a cross - sectional view showing another example of a coated sheet that may be assembled to the steel structure shown in FIG. 1A. [Figure 3] FIG. 3 is a diagram for explaining a method of measuring the storage modulus of the bonding layer. [Figure 4A] FIG. 4A is a diagram for explaining a repair method of a steel structure. [Figure 4B] FIG. 4B is a diagram for explaining a repair method of a steel structure. [Figure 4C] FIG. 4C is a diagram for explaining a repair method of a steel structure. [Figure 4D] FIG. 4D is a diagram for explaining a repair method of a steel structure. [Figure 5] FIG. 5 is a cross - sectional view showing still another example of a steel structure. [Figure 6] FIG. 6 is a diagram for explaining a method of measuring tack.

Embodiments for Carrying Out the Invention

[0013] One embodiment of the present disclosure relates to the following <1> to <34>.

[0014] <1> A process for preparing the surface of deteriorated parts of steel structures, including steel materials, The process of applying paint to the steel material to form a coating film, A step of drying the coating film until the tack of the coating film becomes 2.0 N / φ5 mm or less, A method for repairing a steel structure, comprising the step of joining a coating sheet to the coating film using a bonding layer contained in the coating sheet.

[0015] <2> The drying step includes a step of evaluating the tack of the coating film. <1> Repair method for steel structures as described above.

[0016] <3> A process for preparing the surface of deteriorated parts of steel structures, including steel materials, The process of applying paint to the steel material to form a coating film, The process of drying the aforementioned coating for two hours or more, A method for repairing a steel structure, comprising the step of joining a coating sheet to the coating film using a bonding layer contained in the coating sheet.

[0017] <4> The tack of the bonding layer is greater than the tack of the paint. <1> or <2> Repair method for steel structures as described above.

[0018] <5> In the drying process, the coating film is dried so that the tack of the coating film is 0.38 N / φ5 mm or more and 2.0 N / φ5 mm or less. <1> , <2> or <4> Repair method for steel structures as described above.

[0019] <6> The total light transmittance of the aforementioned covering sheet is 70% or more. <1> ~ <5> A method for repairing steel structures as described in any of the following.

[0020] <7> The haze transmitted through the aforementioned covering sheet is 97% or less. <1> ~ <6> A method for repairing steel structures as described in any of the following.

[0021] <8> The bonding layer contains an acrylic adhesive. <1> ~ <7> A method for repairing steel structures as described in any of the following.

[0022] <9> The aforementioned paint is a two-component, solvent-based paint. <1> ~ <8> A method for repairing steel structures as described in any of the following.

[0023] <10> The aforementioned covering sheet contains an ultraviolet absorber, The maximum spectral transmittance of the coated sheet at wavelengths between 300 nm and 350 nm is 1% or less. <1> ~ <9> A method for repairing steel structures as described in any of the following.

[0024] <11> The aforementioned paint is an epoxy resin paint. <1> ~ <10> A method for repairing steel structures as described in any of the following.

[0025] <12> The aforementioned paint is a urethane resin paint or a fluororesin paint. <1> ~ <10> A method for repairing steel structures as described in any of the following.

[0026] <13> The water vapor permeability of the coating sheet under conditions of 40°C and 90% RH is 3.0 g / (m²). 2 • day) is less than or equal to <1> ~ <12> A method for repairing steel structures as described in any of the following.

[0027] <14> The oxygen permeability of the covering sheet under conditions of 23°C and 60% RH is 6.57 cc / (m²·day·atm) or less. <1> ~ <13> A method for repairing steel structures as described in any of the following.

[0028] <15> The process of applying paint to steel material to form a coating, A step of drying the coating film until the tack of the coating becomes 2.0 N / φ5 mm or less, A method for manufacturing a steel structure, comprising the step of joining the coating sheet to the coating film using the bonding layer contained in the coating sheet.

[0029] <16> The drying step includes a step of evaluating the tack of the coating film. <15> A method for manufacturing steel structures as described above.

[0030] <17> The process of applying paint to steel material to form a coating, The process of drying the aforementioned coating for two hours or more, A method for manufacturing a steel structure, comprising the step of joining the coating sheet to the coating film using the bonding layer contained in the coating sheet.

[0031] <18> The tack of the bonding layer is greater than the tack of the paint. <15> or <16> A method for manufacturing steel structures as described above.

[0032] <19> In the drying process, the coating film is dried so that the tack of the coating film is 0.38 N / φ5 mm or more and 2.0 N / φ5 mm or less. <15> , <16> or <18> A method for manufacturing steel structures as described above.

[0033] <20> The total light transmittance of the aforementioned covering sheet is 70% or more. <15> ~ <19> A method for manufacturing a steel structure as described in any of the above.

[0034] <21> The haze transmitted through the aforementioned covering sheet is 97% or less. <15> ~ <20> A method for manufacturing a steel structure as described in any of the above.

[0035] <22> The bonding layer contains an acrylic adhesive. <15> ~ <21> A method for manufacturing a steel structure as described in any of the above.

[0036] <23> The aforementioned paint is a two-component, solvent-based paint. <15> ~ <22> A method for manufacturing a steel structure as described in any of the above.

[0037] <24> The aforementioned covering sheet contains an ultraviolet absorber, The maximum spectral transmittance of the coated sheet at wavelengths between 300 nm and 350 nm is 1% or less. <15> ~ <23> A method for manufacturing a steel structure as described in any of the above.

[0038] <25> The aforementioned paint is an epoxy resin paint. <15> ~ <24> A method for manufacturing a steel structure as described in any of the above.

[0039] <26> The aforementioned paint is a urethane resin paint or a fluororesin paint. <15> ~ <24> A method for manufacturing a steel structure as described in any of the above.

[0040] <27> The water vapor permeability of the coating sheet under conditions of 40°C and 90% RH is 3.0 g / (m²). 2 • day) is less than or equal to <15> ~ <26> A method for manufacturing a steel structure as described in any of the above.

[0041] <28> The oxygen permeability of the covering sheet under conditions of 23°C and 60% RH is 6.57 cc / (m²·day·atm) or less. <15> ~ <27> A method for manufacturing a steel structure as described in any of the above.

[0042] <29> Steel materials, The coating film and The covering sheet and the following are included in this order: A steel structure in which the ratio of the peel strength of the coating sheet to the coating film after the weathering test to the initial peel strength of the coating sheet to the coating film is 70% or more.

[0043] <30> The total light transmittance of the aforementioned covering sheet is 70% or more. <29> Steel structures as described above.

[0044] <31> The haze transmitted through the aforementioned covering sheet is 97% or less. <29> or <30> Steel structures as described above. <32> The aforementioned covering sheet contains an ultraviolet absorber, The maximum spectral transmittance of the coated sheet at wavelengths between 300 nm and 350 nm is 1% or less. <29> ~ <31> A steel structure as described in any of the following.

[0045] <33> The water vapor permeability of the coating sheet under conditions of 40°C and 90% RH is 3.0 g / (m²). 2 • day) is less than or equal to <29> ~ <32> A steel structure as described in any of the following.

[0046] <34> The oxygen permeability of the covering sheet under conditions of 23°C and 60% RH is 6.57 cc / (m²·day·atm) or less. <29> ~ <33> A method for manufacturing a steel structure as described in any of the above.

[0047] The following describes in detail one embodiment of the present disclosure. In the drawings attached to this specification, the scale and aspect ratios have been appropriately changed and exaggerated from those of the actual objects for the sake of ease of understanding.

[0048] In this specification, terms such as "film," "sheet," and "board" are not distinguished from each other solely on the basis of differences in name. For example, a "repair sheet" cannot be distinguished solely from a component called a repair film or repair board based on differences in name.

[0049] In this specification, the normal direction of a film-like (sheet-like, plate-like) member refers to the direction parallel to the normal or perpendicular to the film surface (sheet surface, plate surface) of the film-like (sheet-like, plate-like) member in question. The "film surface (sheet surface, plate surface)" refers to the surface that coincides with the film-like (sheet-like, plate-like) member in question when viewed as a whole and in a broad sense. Figures 1A to 2B all show cross-sections along the normal direction of the covering sheet.

[0050] In this specification, multiple candidate upper limits and multiple candidate lower limits for a numerical range may be described in separate statements. In such statements, the numerical range may be constructed by combining any one candidate upper limit and any one candidate lower limit. As an example, consider the statement, "Parameter B may be greater than or equal to A1, greater than or equal to A2, greater than or equal to A3. Parameter B may be less than or equal to A4, less than or equal to A5, or less than or equal to A6." In this example, the numerical range of parameter B may be greater than or equal to A1 and less than or equal to A4, greater than or equal to A1 and less than or equal to A5, greater than or equal to A1 and less than or equal to A6, greater than or equal to A2 and less than or equal to A4, greater than or equal to A2 and less than or equal to A5, greater than or equal to A2 and less than or equal to A6, greater than or equal to A3 and less than or equal to A4, greater than or equal to A3 and less than or equal to A5, or greater than or equal to A6.

[0051] <<<Steel structures>>> As shown in Figures 1A and 1B, the steel structure 10 includes steel material 20, a coating 15, and a covering sheet 30 in that order. The coating 15 is located between the steel material 20 and the covering sheet 30 in the lamination direction. The covering sheet 30 is in contact with the coating 15. The covering sheet 30 is attached to the coating 15. The covering sheet 30 includes a bonding layer 35. The covering sheet 30 is attached to the coating using the bonding layer 35. The coating 15 may be in contact with the steel material 20.

[0052] In the example shown in Figure 1A, the steel structure 10 includes, in this order, steel material 20, a rust-preventive layer 18 as a coating 15, and a covering sheet 30. In the example shown in Figure 1A, the covering sheet 30 is in contact with the rust-preventive layer 18. In the example shown in Figure 1A, the covering sheet 30 is attached to the rust-preventive layer 18.

[0053] As shown in Figure 1B, the steel structure 10 may include multiple coatings 15 between the steel material 20 and the coating sheet 30. In the example shown in Figure 1B, the steel structure 10 includes the steel material 20, a rust-preventive layer 41, a first undercoat layer 42, a second undercoat layer 43, an intermediate coat layer 44, a topcoat layer 45, and a coating sheet 30 in this order. In the example shown in Figure 1B, the topcoat layer 45 constitutes the coating 15. In the example shown in Figure 1B, the coating sheet 30 is in contact with the topcoat layer 45 which constitutes the coating 15. In the example shown in Figure 1B, the coating sheet 30 is attached to the topcoat layer 45 which constitutes the coating 15.

[0054] The steel structure 10 may include further layers. For example, as shown by the dashed line in Figure 1A, the steel structure 10 may include a topcoat layer 19 that constitutes the outermost layer. In this example, the covering sheet 30 may be located between the topcoat layer 19 and the rust-preventive layer 18 in the lamination direction. The topcoat layer 19 shown in Figure 1A may have one or more functions expected of the outermost layer, such as barrier properties, weather resistance, scratch resistance, and strength. The topcoat layer 19 shown in Figure 1A may be a colored coating. The topcoat layer 19 is also applicable to the covering sheet 30 shown in Figure 1B.

[0055] The steel structure 10 is a structure that includes steel materials 20. The steel materials 20 may constitute the base material of the steel structure 10. Examples of steel structures 10 include bridges, bridge piers, steel towers, steel pipes, chimneys, tanks, plants, pipelines, rolled plates, and roofs. Further examples of steel structures 10 include metal casings for vending machines, cubicles (high-voltage power receiving equipment), and photo booths. The steel structure 10 may be, for example, an architectural structure or a civil engineering structure.

[0056] Examples of steel materials 20 include nickel-chromium steel, nickel-chromium-molybdenum steel, chromium steel, chromium-molybdenum steel, and manganese steel alloys, as well as carbon steel. Steel materials 20 can corrode due to corrosive factors such as water and oxygen. Steel materials 20 may have rusted areas on their surface due to corrosion. Examples of rust include red rust such as iron oxide (Fe2O3). The rusted areas or other abnormal parts of the steel materials 20 constitute the deteriorated parts 12 of the steel structure 10.

[0057] The steel structure 10 may include a coating 15 that covers the steel material 20. The coating 15 may be provided for the purpose of suppressing the deterioration of the steel material 20. An example of the coating 15 is the rust-preventive layer 18 shown in Figure 1A. An example of the coating 15 is the rust-preventive layer 41, first undercoat layer 42, second undercoat layer 43, intermediate coat layer 44, and topcoat layer 45 shown in Figure 1B. The coating 15 may develop abnormalities such as cracks and blisters due to aging deterioration or construction or repair work performed on the steel structure. The parts of the coating 15 that have defects such as cracks and blisters also constitute the deteriorated parts 12 of the steel structure.

[0058] <<Covering Sheet>> The coating sheet 30 includes a first surface 31 and a second surface 32. The first surface 31 and the second surface 32 constitute the outermost surface of the coating sheet 30. The coating sheet 30 is in the form of a sheet. The first surface 31 and the second surface 32 constitute a pair of main surfaces of the coating sheet 30. The first surface 31 and the second surface 32 face each other in the lamination direction of the steel material 20, the coating film 15, and the coating sheet 30. The first surface 31 and the second surface 32 face each other in the thickness direction of the coating sheet 30.

[0059] The first surface 31 is further away from the steel material 20 than the second surface 32. The second surface 32 is closer to the steel material 20 than the first surface 31. The covering sheet 30 is in contact with the coating film 15 on the second surface 32. The covering sheet 30 is bonded to the coating film 15 on the second surface 32.

[0060] The covering sheet 30 is used to cover the steel material 20. The covering sheet 30 may protect the steel material 20 by covering it. The covering sheet 30 may suppress the deterioration of the steel material 20. The covering sheet 30 may be laminated onto the steel material 20 when the steel structure 10 is newly constructed. The covering sheet 30 may be used to repair a steel structure 10 that has deteriorated parts 12. The covering sheet 30 used for repair may be laminated onto the part of the steel structure 10 from which the deteriorated parts 12 have been removed.

[0061] The peel strength immediately after bonding the coating sheet 30 to the coating film, specifically after being left for 24 hours or more, is called the initial peel strength. From the viewpoint of ensuring strong adhesion between the coating sheet 30 and the coating film 15, the initial peel strength may be 7.5 N / 10 mm or higher, 10 N / 10 mm or higher, or 12.5 N / 10 mm or higher. There is no particular upper limit set for the initial peel strength. The initial peel strength may be 30 N / 10 mm or lower, or 20 N / 10 mm or lower.

[0062] In this embodiment, as will be described in detail later, we propose shortening the drying time of the coating film when preparing the coating film to which the covering sheet 30 is joined. The initial peel strength increases as the drying time increases, at least in the initial stages of the drying process of the coating film. On the other hand, the inventors have confirmed that when the coating film is dried for a long time, the peel strength can decrease significantly from the initial peel strength as the period of use increases. After further intensive research by the inventors, it was confirmed that the decrease in peel strength can be suppressed by shortening the drying time of the coating film 15 to which the covering sheet 30 is joined. It was also confirmed that the decrease in peel strength can be suppressed by setting a lower limit on the tack of the coating film 15 to which the covering sheet 30 is joined.

[0063] More specifically, in this embodiment, the ratio of the peel strength after a weathering test under the following conditions to the initial peel strength of the covering sheet 30 against the coating film 15 was made 70% or more. Furthermore, the ratio of the peel strength after a weathering test to the initial peel strength in steel structures may be 70% or more, 75% or more, or 80% or more. By setting a lower limit on the ratio of the peel strength after a weathering test to the initial peel strength in steel structures, the covering sheet 30 can be stably bonded to the coating film 15 over a long period of time.

[0064] There is no specific upper limit set for the ratio of the peel strength after weathering testing to the initial peel strength of steel structures. The ratio of the peel strength after weathering testing to the initial peel strength of steel structures may be 100% or less, or less than 100%.

[0065] It is difficult to measure the peel strength of the coating sheet 30 against the coating film 15 on an actual steel structure 10. Therefore, instead of measuring the peel strength on an actual steel structure 10, the peel strength measured on a test sample will be treated as the peel strength of the coating sheet 30 against the coating film 15 on the steel structure 10. The test sample will be made using SS400 sheet metal, a common structural rolled steel, as the steel material. The thickness of the SS400 sheet metal will be 3.2 mm.

[0066] A test coating film having the same configuration as the actual coating film included in the steel structure 10 to be evaluated is fabricated on an SS400 plate using the same materials and the same manufacturing method as the actual coating film. Furthermore, a test coating sheet having the same configuration as the actual coating sheet included in the steel structure 10 to be evaluated is bonded to the test coating film fabricated on the SS400 plate using the same bonding method as the actual coating sheet. In this way, a test sample including the SS400 plate, the test coating film, and the test coating sheet is fabricated. By testing the test sample, the initial peel strength (N / 10mm) of the steel structure 10 to be evaluated is determined. A weathering test is performed on the test sample, and by further testing the test sample after the weathering test, the peel strength (N / 10mm) of the steel structure 10 to be evaluated after the weathering test is determined.

[0067] The peel strength is determined by the peel strength test described below. The peel strength is determined by a 180-degree peel test in accordance with JIS Z0237:2022 Method 1, except for the matters specified below.

[0068] The peel strength test is performed using a tensile testing apparatus. The test sample size is 100 mm wide x 70 mm long. At one longitudinal end of the test sample, the coating sheet is not bonded to the coating film. The coating sheet that is not bonded to the coating film is folded 180° relative to the rest of the test sample. The coating sheet that is not bonded to the coating film is held by one grip of the tensile testing machine. The other longitudinal end of the test sample is held by the other grip of the tensile testing machine.

[0069] Move one gripper and the other gripper relative to each other so that they move away from each other. The relative movement speed is set to 300 mm / min. The relative movement of one gripper and the other gripper is used to peel the coating sheet from the coating film. The length to be peeled is 50 mm along the longitudinal direction of the test sample. Measure the peeling load applied to the test sample when peeling 25 mm, excluding the initial 25 mm. Calculate the arithmetic mean of the peeling load over the 50 mm peeling period. Of the calculated average peeling load, the load applied to a width of 10 mm is taken as the measured peeling strength for the test sample.

[0070] For the peel strength test, three test samples are prepared for the steel structure to be evaluated. The peel strength test is performed on the three test samples. The arithmetic mean of the peel strength measurements for the three test samples is taken as the peel strength (N / 10mm) of the steel structure to be evaluated.

[0071] The total light transmittance of the covering sheet may be 70% or higher, 80% or higher, or 85% or higher. By setting a lower limit for the total light transmittance, the condition of the steel material 20 can be easily observed through the covering sheet 30. Therefore, inspection of the steel material 20 can be facilitated.

[0072] There is no particular upper limit to the total light transmittance of the covering sheet 30. The total light transmittance of the covering sheet 30 may be 100% or less, or less than 100%.

[0073] A D65 light source is used to measure total light transmittance. Before measuring total light transmittance, the D65 light source is lit for 15 minutes to stabilize its output. The angle of incidence to the sample when measuring total light transmittance is 0°. The incident surface when measuring the total light transmittance of the covering sheet 30 is the first surface 31 of the covering sheet 30. The test environment when measuring total light transmittance is a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample is placed in the test environment for 16 hours before the start of the test. Other measurement conditions when measuring total light transmittance are in accordance with JIS K7361-1:1997.

[0074] The total light transmittance shall be the arithmetic mean of the five measured values. The five measured values ​​shall be those taken at five measurement locations on the covering sheet 30 to be evaluated. The five measurement locations shall be located at least 10 mm apart from each other.

[0075] The haze transmitted through the covering sheet 30 may be 97% or less, 90% or less, 86% or less, 85% or less, 80% or less, or 75% or less. By setting an upper limit on the haze transmitted, the condition of the steel material 20 can be easily observed through the covering sheet 30. Therefore, inspection of the steel material 20 through the covering sheet 30 can be facilitated.

[0076] The haze transmitted through the coating sheet does not have a lower limit. The haze transmitted through the coating sheet 30 may be 0% or greater, or it may be greater than 0%.

[0077] A D65 light source is used to measure transmitted haze. Before measuring transmitted haze, the D65 light source is lit for 15 minutes to stabilize its output. The angle of incidence to the sample when measuring transmitted haze is 0°. The incident surface when measuring transmitted haze on the covering sheet 30 is the second surface 32 of the covering sheet 30. The test environment when measuring transmitted haze is 23°C ± 2°C and 50% ± 5% relative humidity. The sample is placed in the test environment for 16 hours before the start of the test. Other measurement conditions when measuring transmitted haze follow JIS K7136:2000.

[0078] The transmitted haze is defined as the arithmetic mean of five measurements. The five measurements are taken at five different measurement locations on the covering sheet 30 being evaluated. The five measurement locations are located at least 10 mm apart from each other.

[0079] The coating sheet 30 may contain an ultraviolet absorber, as described later. The maximum spectral transmittance of the coating sheet 30 containing the ultraviolet absorber at wavelengths of 300 nm to 350 nm may be 1.0% or less, or 0.50% or less. By setting an upper limit on the maximum spectral transmittance in the ultraviolet wavelength range, ultraviolet degradation in outdoor installation applications can be effectively suppressed. Therefore, the coating sheet 30 can protect the steel material 20 and the coating film 15 over a long period of time.

[0080] The maximum transmittance of the coated sheet 30 at wavelengths between 300 nm and 350 nm does not have a lower limit. The maximum transmittance of the coated sheet 30 at wavelengths between 300 nm and 350 nm may be 0% or greater, or it may be greater than 0%.

[0081] The transmittance at each wavelength, i.e., the spectral transmittance, shall be the arithmetic mean of five measured values ​​taken in accordance with JIS Z8722:2009. The five measured values ​​shall be taken at five measurement locations on the sample of the coated sheet 30 to be evaluated. The five measurement locations shall be at least 10 mm apart from each other.

[0082] The wavelengths used for measuring spectral transmittance are wavelengths in the range of 300 nm to 350 nm, at 1 nm intervals. That is, spectral transmittance is measured for light with integer wavelengths (nm) between 300 nm and 350 nm. The geometric condition f specified in JIS Z8722:2009 is adopted for the measurement of spectral transmittance.

[0083] The angle of incidence to the sample when measuring spectral transmittance is set to 0°. The incident surface when measuring spectral transmittance is the first surface 31 of the covering sheet 30.

[0084] The test environment for measuring spectral transmittance shall be a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample shall be placed in the test environment for 16 hours before the start of the test. Before measuring spectral transmittance, the light source of the measuring device shall be turned on for 15 minutes to stabilize the output of the light source.

[0085] <<Layer structure of the covering sheet>> The covering sheet 30 includes one or more functional layers and a bonding layer 35. The functional layers perform the functions expected of a covering sheet that covers the steel material 20. The bonding layer 35 constitutes one of the outermost surfaces of the covering sheet 30. The bonding layer 35 is in contact with the coating film 15. The bonding layer 35 is bonded to the coating film 15. The functional layers are maintained in a state of covering the steel material 20 by the bonding layer 35. The bonding layer 35 bonds the covering sheet 30 to the coating film 15 on the steel material 20. As described above, examples of the coating film 15 include a rust-preventive layer 18 and a topcoat layer 45.

[0086] As shown in Figure 2A, the covering sheet 30 may include a bonding layer 35, a base material 33, and a weather-resistant layer 34 in the order from the second surface 32 to the first surface 31 in the lamination direction. That is, the covering sheet shown in Figure 2A includes the base material 33 and the weather-resistant layer 34 as functional layers. The covering sheet 30 shown in Figure 2A may be included in the steel structure 10 shown in Figure 1. In the example shown in Figure 2A, the weather-resistant layer 34 constitutes the first surface 31. The bonding layer 35 constitutes the second surface 32.

[0087] As shown in Figure 2B, the covering sheet 30 may include a barrier layer 36. The covering sheet 30 may include the barrier layer 36 and the base material 33 in the order from the second surface 32 to the first surface 31 in the lamination direction. The covering sheet 30 shown in Figure 2B includes a bonding layer 35, a barrier layer 36, a second bonding layer 37, a base material 33, and a weather-resistant layer 34 in the order from the second surface 32 to the first surface 31 in the lamination direction. The covering sheet 30 shown in Figure 1B may be included in the steel structure 10 shown in Figure 1. In the example shown in Figure 2B, the weather-resistant layer 34 constitutes the first surface 31. The bonding layer 35 constitutes the second surface 32. In the example shown in Figure 2B, the second bonding layer 37 may be omitted.

[0088] Each layer that may be included in the covering sheet 30 will be described in more detail below.

[0089] <Base material> The base material 33 may be a resin film. Examples of resin materials constituting the base material 33 include polyolefins such as polyethylene and polypropylene, polyvinyl chloride, vinylidene chloride-vinyl chloride copolymer, polyesters such as polyethylene terephthalate, polycarbonate, polyarylate, styrene resin, acrylic resin, acrylic urethane resin, urethane resin, fluororesin, acetylcellulose, polyamide, and polyimide. The base material 33 may be a single layer or a multilayer. The base material 33 may also be a laminated film of resin films.

[0090] The base material 33 may have a cellular structure. The cellular structure may be a closed-cell structure, a continuous-cell structure, or a semi-continuous semi-closed-cell structure in which closed-cell and continuous-cell structures are mixed. An example of a base material 33 having a cellular structure is a foam layer. More specifically, examples of base material 33 include acrylic resin foam (acrylic foam), urethane resin foam (urethane foam), polyolefin foam, and rubber foam containing acrylic rubber and other elastomers.

[0091] The base material 33 may contain additives. Examples of additives include pigments, dyes, colorants, antistatic agents, flame retardants, fungicides, plasticizers, leveling agents, flow regulators, defoamers, and dispersants. The base material 33 may also contain weather-resistant agents such as ultraviolet absorbers, antioxidants, and light stabilizers. The base material 33 containing weather-resistant agents has excellent weather resistance. Because the base material 33 has weather resistance, the topcoat layer described later may be made thinner, or the topcoat layer may be omitted.

[0092] The thickness of the base material 33 may be determined considering the finish after repair of the steel structure, that is, the finish after the covering sheet 30 is attached to the steel material 20, as well as the handling and ease of application of the covering sheet 30. The thickness of the base material 33 may be 10 μm or more, 20 μm or more, 30 μm or more, 50 μm or more, or 100 μm or more. The thickness of the base material 33 may be 5000 μm or less, 4000 μm or less, 3000 μm or less, 2000 μm or less, or 1000 μm or less.

[0093] The base material 33 may include a fiber-reinforced resin layer. The fiber-reinforced resin layer can improve the impact resistance of the base material 33 and the covering sheet 30. The fiber-reinforced resin layer may include a resin material and reinforcing fibers. Examples of the resin material include the resin materials that can be used in the base material 33 described above. The reinforcing fibers may be inorganic fibers or organic fibers. Examples of inorganic fibers include glass fibers, carbon fibers, silicon-titanium-carbon fibers, boron fibers, and metal fibers. Examples of organic fibers include aramid fibers, vinylon fibers, polyester fibers, and polyamide fibers. The reinforcing fibers may be in a mesh (network) form. The fiber-reinforced resin layer may include a glass mesh as the reinforcing fibers.

[0094] The thickness of the fiber-reinforced resin layer may be 50 μm or more, 75 μm or more, 100 μm or more, 125 μm or more, or 150 μm or more. The thickness of the fiber-reinforced resin layer may be 550 μm or less, 525 μm or less, 500 μm or less, 475 μm or less, or 450 μm or less. By setting the thickness of the fiber-reinforced resin layer in this way, impact resistance can be imparted to the covering sheet 30.

[0095] The base material 33 may include a laminate containing a fiber-reinforced resin layer and a resin layer. The base material 33 may include a laminate containing a first resin layer, a fiber-reinforced resin layer, and a second resin layer. Examples of resin materials that can be used in the base material 33 described above are given as resin materials constituting the resin layer, the first resin layer, and the second resin layer. The laminate included in the base material 33 may include a fiber-reinforced resin layer containing polyethylene and a glass mesh, and a polyethylene layer. The laminate included in the base material 33 may include a first polyethylene layer, a fiber-reinforced resin layer containing polyethylene and a glass mesh, and a second polyethylene layer.

[0096] The thickness of the resin layer, the thickness of the first resin layer, and the thickness of the second resin layer may be 10 μm or more, 20 μm or more, 30 μm or more, 50 μm or more, or 100 μm or more, respectively. The thickness of the resin layer, the thickness of the first resin layer, and the thickness of the second resin layer may be 1000 μm or less, 800 μm or less, 600 μm or less, 500 μm or less, or 400 μm or less, respectively.

[0097] <Weatherproof layer> The weather-resistant layer 34 is a layer that has weather resistance. The weather-resistant layer 34 may contain a binder resin and a weather-resistant agent. The weather-resistant layer 34 may contain one or more of the following as a weather-resistant agent: an ultraviolet absorber, an antioxidant, and a light stabilizer.

[0098] The weather-resistant layer 34 may contain a cured resin as a binder resin. The cured resin is a cured product of a curable resin composition. The curable resin composition may be a thermosetting resin composition. The curable resin composition may be an ionizing radiation-curable resin composition. The weather-resistant layer 34 may contain a cured product of a curable resin composition and a cured product of an ionizing radiation-curable resin composition.

[0099] The thermosetting resin composition contains a thermosetting resin. The thermosetting resin composition hardens upon heating. Examples of thermosetting resins include unsaturated group-containing (meth)acrylic resins, unsaturated polyesters, urethane resins, epoxy resins, phenolic resins, aminoalkyd resins, urea resins, melamine resins, melamine-urea cocondensation resins, guanamine resins, diallyl phthalate resins, and silicone resins.

[0100] The thermosetting resin composition may contain a curing agent along with the thermosetting resin. In the case of unsaturated group-containing (meth)acrylic resins and unsaturated polyesters, peroxides such as methyl ethyl ketone peroxide or radical initiators such as azoisobutylnitrile may be used. In the case of urethane resins, isocyanate-based curing agents may be used. In the case of epoxy resins, organic amine-based curing agents may be used.

[0101] The thermosetting resin may be a two-component curing urethane resin, with a polyol as the main component and an isocyanate compound as the curing agent. Examples of polyols include (meth)acrylic polyol, polyether polyol, polyester polyol, polyethylene glycol, and polypropylene glycol. The isocyanate compound is a polyvalent isocyanate having two or more isocyanate groups. Examples of isocyanate compounds include aromatic isocyanates such as 4,4-diphenylmethane diisocyanate; and aliphatic (or alicyclic) isocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated diphenylmethane diisocyanate.

[0102] In one specific example of the weather-resistant layer 34, the cured resin product contained in the weather-resistant layer 34 may be a cross-linked cured product of (meth)acrylic polyol using an isocyanate-based curing agent.

[0103] The ionizing radiation-curable resin composition contains a compound having an ionizing radiation-curable functional group. Hereinafter, the compound having an ionizing radiation-curable functional group will also be referred to as the "ionizing radiation-curable compound." The ionizing radiation-curable functional group is a group that crosslinks upon irradiation with ionizing radiation.

[0104] Ionizing radiation may be electromagnetic waves or charged particle beams. Ionizing radiation has energy quanta that can polymerize or crosslink molecules. Examples of ionizing radiation include ultraviolet (UV), electron beams (EB), X-rays, gamma rays, alpha rays, and ion beams. In the example where the weather-resistant layer 34 contains an ultraviolet absorber as a weathering agent, the ionizing radiation may be an electron beam.

[0105] Examples of ionizing radiation-curable functional groups include ethylenically unsaturated bonding groups such as (meth)acryloyl groups, vinyl groups, and allyl groups, as well as epoxy groups and oxetanyl groups. Ionizing radiation-curable compounds may contain ethylenically unsaturated bonding groups. Ionizing radiation-curable compounds may contain two or more ethylenically unsaturated bonding groups. Ionizing radiation-curable compounds may also be polyfunctional (meth)acrylate compounds containing two or more ethylenically unsaturated bonding groups. Polyfunctional (meth)acrylate compounds may contain either monomers or oligomers.

[0106] Examples of polymerizable monomers include (meth)acrylate monomers having a (meth)acryloyl group in the molecule, and polyfunctional (meth)acrylate monomers having two or more (meth)acryloyl groups in the molecule. The number of (meth)acryloyl groups in the polyfunctional (meth)acrylate monomer may be between 2 and 8, or between 2 and 6.

[0107] As polymerizable monomers, difunctional (meth)acrylates such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol A tetraethoxy di(meth)acrylate and bisphenol A tetrapropoxy di(meth)acrylate; trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, penta Examples include trifunctional or more (meth)acrylates such as erythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; and ethylene oxide modified, propylene oxide modified, caprolactone modified, isocyanuric acid modified, or propionic acid modified versions of these (meth)acrylates.

[0108] Examples of polymerizable oligomers include (meth)acrylate oligomers having two or more (meth)acryloyl groups in the molecule. Examples of (meth)acrylate oligomers include urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, polycarbonate (meth)acrylate, polycaprolactone urethane (meth)acrylate, polycaprolactone diol urethane (meth)acrylate, and acrylic (meth)acrylate. The number of (meth)acryloyl groups in the polymerizable oligomer may be 2 to 8, or 2 to 6.

[0109] Examples of polymerizable oligomers include highly hydrophobic polybutadiene (meth)acrylate oligomers having (meth)acryloyl groups in the side chains of polybutadiene oligomers, and silicone (meth)acrylate oligomers having polysiloxane bonds in the main chain.

[0110] The weight-average molecular weight of the polymerizable oligomer may be 500 or more, 1,000 or more, or 2,000 or more. The weight-average molecular weight of the polymerizable oligomer may be 10,000 or less, 8,000 or less, or 6,000 or less. The weight-average molecular weight is the average molecular weight measured by gel permeation chromatography (GPC) analysis and converted to standard polystyrene.

[0111] As ionizing radiation-curable compounds, monofunctional (meth)acrylates may be used along with polyfunctional (meth)acrylates. In this example, the viscosity of the curable composition during coating can be reduced. Examples of monofunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and isobornyl (meth)acrylate.

[0112] If the ionizing radiation-curable compound is an ultraviolet-curable compound, at least one selected from photopolymerization initiators and photopolymerization accelerators may be used together with the ultraviolet-curable compound.

[0113] The weather-resistant layer 34 may contain cured products of curable compounds, or cured products of ionizing radiation-curable compositions, from the viewpoint of having excellent heat resistance, scratch resistance, and stain resistance. A coating solution containing an electron beam-curable compound can be solvent-free and does not require a photopolymerization initiator. Electron beam-curable compounds provide stable curing characteristics. Furthermore, electron beam-curable compounds can stably retain additives such as weathering agents, for example, ultraviolet absorbers, through crosslinking. Therefore, ultraviolet This allows for stable suppression of bleed-out of additives such as absorbents. This prevents the excellent weather resistance of the weather-resistant layer 34 from deteriorating over time. For these reasons, preferably, the weather-resistant layer 34 contains a cured product of an electron beam-curable compound. The ionizing radiation-curable compound may be a polymerizable oligomer, a (meth)acrylate oligomer having two or more (meth)acryloyl groups in the molecule, or a urethane (meth)acrylate.

[0114] The proportion of cured resin in relation to the total resin components in the weather-resistant layer 34 may be 50% by mass or more, 70% by mass or more, 80% by mass or more, or 90% by mass or more.

[0115] The weather-resistant layer 34 can be produced by forming a coating film of a coating solution containing a curable resin composition and curing the coating film. In an example where the weather-resistant layer 34 contains a cured product of an electron beam-curable resin composition, the coating film is irradiated with an electron beam. A portion of this electron beam penetrates the coating film and irradiates the substrate 33. In this example, the substrate 33 may contain a polyolefin. The polyolefin is partially crosslinked by the electron beam. The crosslinking of the polyolefin improves the heat resistance of the substrate 33.

[0116] The polyolefin-containing substrate 33 exhibits improved adhesion to the weather-resistant layer 34 containing the cured product of the electron beam-curable resin composition compared to a substrate containing a fluororesin. Furthermore, by using polyolefin instead of fluororesin in the substrate 33, the generation of PFAS as an impurity can be suppressed. PFAS, as an artificial organofluorine compound, is a cause for concern due to its bioaccumulation potential. Suppressing the generation of PFAS can contribute to reducing environmental impact.

[0117] From the above points, in combination with a weather-resistant layer 34 containing a cured product of an electron beam-curable resin composition, the base material 33 may also contain a polyolefin. Examples of polyolefins used in the base material 33 include polyethylene, polypropylene, polybutene, and polymethylpentene.

[0118] Examples of polypropylene include copolymers such as propylene homopolymers, ethylene-propylene copolymers, propylene-butene copolymers, and ethylene-propylene-butene copolymers. For the polypropylene contained in the base material 33, propylene homopolymers, ethylene-propylene copolymers, and propylene-butene copolymers are preferred.

[0119] From the viewpoint of processability, the polyolefin content in the base material 33 may be 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass or more, relative to the total resin components of the base material 33.

[0120] <Barrier layer> The barrier layer 36 may be a vapor-deposited film formed on a resin film. The covering sheet 30 may include a barrier film comprising the barrier layer 36 and the resin film. The barrier layer 36 may be a vapor-deposited film formed on a substrate 33. When the barrier layer 36 together with the substrate 33 constitutes a barrier film, the second bonding layer 37 shown in Figure 2B may be omitted.

[0121] The coating sheet 30 including the barrier layer 36 may have excellent gas barrier properties. The coating sheet 30 including the barrier layer 36 may have at least one of excellent oxygen barrier properties and excellent water vapor barrier properties. The coating sheet 30 including the barrier layer 36 can suppress rusting of the steel material 20 and deterioration of the coating film on the steel material 20.

[0122] An example of a resin film used in a barrier film is the resin film that constitutes the base material 33 described above. The thickness of the resin film may be 5 μm or more, 10 μm or more, 100 μm or less, or 50 μm or less.

[0123] The barrier layer 36 may be a vapor-deposited film containing one or more metals, a vapor-deposited film containing one or more inorganic oxides, or a vapor-deposited film containing one or more metals and one or more inorganic oxides. Examples of metals to be included in the vapor-deposited film include aluminum, chromium, tin, nickel, copper, silver, gold, and platinum. Examples of inorganic oxides include aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, barium oxide, and silicon carbide oxide (carbon-containing silicon oxide). Specifically, the barrier layer 36 may contain one or more aluminum vapor-deposited films, aluminum oxide (alumina) vapor-deposited films, and silicon oxide (silica) vapor-deposited films.

[0124] The thickness of the deposited film may be 1 nm or more, 5 nm or more, or 10 nm or more. The thickness of the deposited film may be 150 nm or less, 100 nm or less, or 80 nm or less.

[0125] The vapor-deposited film constituting the barrier layer 36 may be formed by physical vapor deposition (PVD) methods such as vacuum deposition, sputtering, and ion plating. The vapor-deposited film constituting the barrier layer 36 may also be formed by chemical vapor deposition (CVD) methods such as plasma chemical vapor deposition, thermochemical vapor deposition, and photochemical vapor deposition.

[0126] Examples of vapor-deposited films include vapor-deposited polyester films such as vapor-deposited polyethylene terephthalate film, vapor-deposited polyamide film, and vapor-deposited OPP film (vapor-deposited biaxially oriented polypropylene).

[0127] A layer containing an ultraviolet absorber may be located between the barrier layer 36 and the first surface 31. The barrier layer 36 may degrade over time due to ultraviolet light. Therefore, the layer containing the ultraviolet absorber can suppress the degradation of the barrier layer 36 and maintain its gas barrier properties. In the example shown in Figure 3C, one or more of the weather-resistant layer 34, the substrate 33, and the second bonding layer 37 may contain an ultraviolet absorber.

[0128] The covering sheet 30 shown in Figure 2B includes a barrier layer 36 and a weather-resistant layer 34, arranged in the order from the second surface 32 to the first surface 31. The barrier layer 36 is located between the steel material 20 and the weather-resistant layer 34 in the lamination direction. The weather-resistant layer 34, which contains weather-resistant agents such as ultraviolet absorbers, maintains the gas barrier properties of the barrier layer 36.

[0129] The oxygen permeability (OTR, unit: cc / (m2·day·atm)) of the coating sheet 30 including the barrier layer 36 may be 6.57 or less, 3.0 or less, or 2.0 or less. By using a coating sheet 30 with such adjusted oxygen permeability, corrosion of the steel material 20 and deterioration of the coating film can be suppressed. A lower oxygen permeability of the coating sheet 30 is preferable, but it may be 0.01 or more, 0.05 or more, or 0.1 or more.

[0130] The oxygen permeability was measured in accordance with JIS K7126-2:2006 "Appendix A (Normative): Test method for oxygen gas permeability by electrolytic sensor method" under conditions of a temperature of 23°C and a relative humidity difference of 60%RH. The covering sheet 30 is installed in the measuring device with the first surface 31 facing the oxygen supply side. The oxygen permeability measuring device may also be the "OX-TRAN 2 / 20" manufactured by MOCON, Inc., USA.

[0131] The oxygen permeability shall be the arithmetic mean of five measured values. The five measured values ​​shall be those taken at five measurement locations on the covering sheet 30 to be evaluated. The five measurement locations shall be located at least 10 mm apart from each other.

[0132] The water vapor permeability (WVTR, unit: g / (m2·day)) of the coating sheet 30 including the barrier layer 36 may be 3.0 or less, 2.5 or less, or 2.0 or less. By using a coating sheet 30 with such adjusted water vapor permeability, corrosion of the steel material 20 and deterioration of the coating film can be suppressed. A lower water vapor permeability of the coating sheet 30 is preferable, but it may be 0.01 or more, 0.05 or more, or 0.1 or more.

[0133] The water vapor transmission rate is measured in accordance with JIS K7129-2:2019 under conditions of 40°C and a relative humidity difference of 90%RH. The covering sheet 30 is installed on the measuring device with the first surface 31 facing the hydrogen supply side. The water vapor transmission rate measuring device may also be a PERMATRAN-w 3 / 33 manufactured by MOCON, Inc., USA.

[0134] The water vapor transmission rate shall be the arithmetic mean of five measured values. The five measured values ​​shall be those taken at five measurement locations on the covering sheet 30 to be evaluated. The five measurement locations shall be located at least 10 mm apart from each other.

[0135] Furthermore, if the rust-preventive layer 18 contains a moisture-curing resin, the coating sheet 30 may have oxygen permeability. If the rust-preventive layer 18 contains a moisture-curing resin, the barrier layer 36 may have only water vapor barrier properties among oxygen barrier properties and water vapor barrier properties. If the rust-preventive layer 18 contains a moisture-curing resin, the oxygen permeability (OTR, unit: cc / (m2·day·atm)) of the coating sheet 30 including the barrier layer 36 may be 100 or more, 250 or more, or 500 or more. By adjusting the oxygen permeability, it is possible to suppress the retention of carbon dioxide gas generated from the rust-preventive layer 18 containing the moisture-curing resin in the coating sheet 30, as described later. Therefore, the coating sheet 30 can adhere closely to the rust-preventive layer 18. In addition, by reducing the retention of air bubbles, the transmission haze of the coating sheet 30 decreases and the total light transmittance increases. Therefore, the transparency of the coating sheet 30 is improved, and the condition of the steel material 20 and the coating film 15 can be observed through the coating sheet 30.

[0136] <Joining layer> The bonding layer 35 and the second bonding layer 37 contain adhesive or tacky components. The bonding layer 35 bonds the coating sheet 30 to the coating film on the steel material 20. The second bonding layer 37 bonds the barrier layer 36 to the substrate 33.

[0137] The bonding layer 35 and the second bonding layer 37 may be adhesive layers or tacky layers. Examples of adhesive or tacky components include acrylic resin, vinyl chloride-vinyl acetate copolymer, vinyl acetate resin, polyolefin, polyester, polyurethane, silicone resin, and rubber resin.

[0138] The bonding layer 35 and the second bonding layer 37 may be pressure-sensitive adhesive layers, i.e., tacky layers. The tacky layer contains an adhesive. That is, the tacky layer may be a layer formed by an adhesive (pressure-sensitive adhesive). The tacky layer exhibits tackiness at room temperature (e.g., 23°C). Examples of adhesives include acrylic adhesives, urethane adhesives, silicone adhesives, and rubber adhesives. Acrylic adhesives are preferred for application to the bonding layer 35 because they have excellent adhesion to the coating film 15 on the steel material 20. Acrylic adhesives also have excellent stability.

[0139] The bonding layer 35 and the second bonding layer 37 may contain additives. Examples of additives include pigments, dyes, colorants, antistatic agents, flame retardants, fungicides, crosslinking agents, tackifiers, plasticizers, leveling agents, flow regulators, defoamers, and dispersants. The bonding layer 35 and the second bonding layer 37 may also contain weather-resistant agents such as UV absorbers, antioxidants, and light stabilizers.

[0140] The storage modulus (G') of the bonding layer 35 and the second bonding layer 37 at 40°C may be 0.05 MPa or more and 1 MPa or less, 0.05 MPa or more and 0.8 MPa or less, 0.1 MPa or more and 1 MPa or less, or 0.1 MPa or more and 0.8 MPa or less. If the storage modulus is above the lower limit, excessive elongation of the adhesive layer when subjected to impact can be suppressed. If the storage modulus is below the upper limit, fracture of the adhesive layer when subjected to impact can be suppressed.

[0141] The storage modulus is measured by the following method: Two test specimens 90 are prepared from the coating sheet 30 according to the method for preparing test specimens described in JIS K7244-1:1998, 6.2. Because they are made from the coating sheet 30, the test specimens 90 include a support 91 corresponding to the portion of the coating sheet 30 other than the bonding layer 35, and an adhesive layer 92 corresponding to the bonding layer 35 of the coating sheet 30.

[0142] Next, the two fabricated test pieces 90 are attached to a measuring device 80 as shown in Figure 3. As shown in Figure 3, the measuring device 80 includes a plate 81 and a jig 82. The jig 82 includes a pair of plate-like portions 83 that sandwich the plate 81. The plate 81 and the pair of plate-like portions 83 extend vertically. The distance between the pair of plate-like portions 83 can be adjusted by rotating a nut 85 screwed onto a bolt 84 that passes through the pair of plate-like portions 83. The bolt 84 does not pass through the plate 81 or the test pieces 90 attached to the measuring device 80. The bolt 84 is located at a different position from the plate 81 and the test pieces 90 in a direction perpendicular to the plane of paper in Figure 3. When attaching the two test pieces 90 to the measuring device 80, first, the two test pieces 90 are bonded to the plate 81 by the action of the adhesive layer 92 so that the plate 81 is sandwiched between the two test pieces 90. Next, by rotating the nut 85, the distance between the pair of plate-like portions 83 is reduced, so that the plate 81 and the two test pieces 90 are sandwiched between the pair of plate-like portions 83, as shown in Figure 3. This fixes the two test pieces 90 to the jig 82.

[0143] Next, the thickness w1 of the test specimen 90 is determined. The thickness w1 of the test specimen 90 can be determined by the following method. Before fixing the two test specimens 90 to the jig 82, the dimensions of the plate 81 and the jig 82 are determined. As dimensions of the plate 81 and the jig 82, the thickness w2 of the plate 81 and the respective thicknesses w3 and w4 of the pair of plate-like portions 83 shown in Figure 3 can be determined. The thicknesses w2, w3, and w4 can be determined by measuring with calipers. Furthermore, after fixing the two test specimens 90 to the jig 82 as shown in Figure 3, the dimensions of the jig 82 with the two test specimens 90 sandwiched between it are determined. As dimensions of the jig 82 with the two test specimens 90 sandwiched between it, the distance w5 from the outer surface of one of the pair of plate-like portions 83 to the outer surface of the other of the pair of plate-like portions 83 shown in Figure 3 can be determined. The distance w5 can be determined by measuring with calipers. Next, the thickness w1 of the test specimen 90 is determined from the dimensions of the plate 81 and the jig 82, and the dimensions of the jig 82 with the two test specimens 90 sandwiched between them. The thickness w1 of the test specimen 90 can be calculated by subtracting the thicknesses w2, w3, and w4 from the distance w5 and dividing by 2. The determined thickness w1 of the test specimen 90 is used to measure the storage modulus (G').

[0144] As shown in Figure 3, after fixing two test specimens 90 to the jig 82, the jig 82 is vibrated in the vertical direction. This applies vertical vibration to the adhesive layer 92 of the test specimen 90. By detecting the movement of the plate 81 when vertical vibration is applied to the adhesive layer 92 of the test specimen 90, the storage modulus (G') of the adhesive layer 92 can be measured.

[0145] The storage modulus (G') is measured under the following conditions. • Atmosphere gas: Nitrogen • Attachment mode: Solid shear mode ·Temperature dependence ·Basic frequency: 10Hz Measurement program: Start temperature = 30°C, Step temperature = 1°C, End temperature = 150°C, Heating rate: 3°C / min) • Sine wave, stop excitation • Manual static load: Adjust to 0g when fixing the two test pieces 90 to the jig 82. • Distortion: A value automatically set when the sample length is entered. 0.05 (Automatic adjustment mode)

[0146] The storage modulus (G') is the arithmetic mean of five measurements. The five measurements are taken at five different measurement locations on the covering sheet 30 being evaluated. The five measurement locations are located at least 10 mm apart from each other.

[0147] The storage modulus (G') can be measured using a solid viscoelasticity analyzer. The Rheogel E4000 manufactured by UBM Co., Ltd. can be used as the solid viscoelasticity analyzer.

[0148] The thickness of the bonding layer 35 and the second bonding layer 37 may be 10 μm or more, 20 μm or more, 30 μm or more, 40 μm or more, or 50 μm or more. The thickness of the bonding layer 35 and the second bonding layer 37 may be 1000 μm or less, 500 μm or less, 300 μm or less, 250 μm or less, 200 μm or less, 180 μm or less, or 150 μm or less.

[0149] The tack of the bonding layer 35 is greater than the tack of the coating film 15, which will be described later. Therefore, the covering sheet can be made to adhere closely to the coating film 15. The tack of the bonding layer 35 is greater than 2.0 N / φ5 mm, and may be 3.0 N / φ5 mm or greater, 4.9 N / φ5 mm or greater, or 5.8 N / φ5 mm or greater. Tack is an index indicating the degree of stickiness. The tack value shall be the value measured by the test method described later. By setting a lower limit for the tack of the bonding layer 35, the covering sheet 30 can be made to adhere closely to the coating film 15. There is no particular upper limit set for the tack of the bonding layer 35. The tack of the bonding layer 35 may be 7.0 or less.

[0150] <Other layers that may be included in the covering sheet> The coating sheet 30 may include further layers, such as a functional layer expected to perform some function, not limited to the examples shown in Figures 2A and 2B. As an example, the coating sheet 30 may further include a release film 38, as shown by the dashed line in Figure 2B. Before joining the coating sheet 30 to the steel material 20, the release film 38 is joined to the joining layer 35. The release film 38 protects the joining layer 35 from foreign matter such as dust before use of the coating sheet 30. When using the coating sheet 30, the release film 38 is removed from the coating sheet 30. With the release film 38 removed, the joining layer 35 is exposed, and the coating sheet 30 can be joined to the steel material 20. Examples of the release film 38 include paper substrates and resin films, as well as those with a release agent applied to their surface. Examples of release agents include silicone release agents, fluorine release agents, and long-chain alkyl release agents.

[0151] <<Rust-preventive layer>> The rust-preventive layer 18 is located between the steel material 20 and the coating sheet 30. The rust-preventive layer 18 suppresses corrosion of the steel material 20. The rust-preventive layer 18 suppresses the spread of corrosion in the steel material 20. As described above, the rust-preventive layer 18 can constitute a coating film 15 to which the coating sheet 30 is attached.

[0152] The rust-preventive layer 18 is produced by applying a rust-preventive paint containing a rust inhibitor to the surface of the steel material 20 to form a coating film, and then drying and solidifying or hardening this coating film. Examples of painting methods include brush painting, roller painting, and spray painting (e.g., air spray, airless spray). The rust-preventive layer 18 formed as a coating film can improve adhesion to the uneven surface of the steel material 20.

[0153] The thickness of the rust-preventive layer 18 may be 10 μm or more, 30 μm or more, 50 μm or more, 100 μm or more, or 150 μm or more. The thickness of the rust-preventive layer 18 may be 1000 μm or less, 800 μm or less, 600 μm or less, or 500 μm or less. By setting a lower limit for the thickness of the rust-preventive layer 18, sufficient rust prevention function can be provided to the rust-preventive layer 18. By setting an upper limit for the thickness of the rust-preventive layer 18, the workability and cost when manufacturing the rust-preventive layer 18 can be improved.

[0154] Examples of rust inhibitors included in the rust-preventive layer 18 include inorganic rust inhibitors and organic rust inhibitors. Inorganic rust inhibitors may be inorganic acids or salts of inorganic acids. Examples of inorganic rust inhibitors include red lead, lead oxide, basic lead chromate, lead dianamid, calcium leadate, basic lead sulfate, zinc chromate, zinc powder, iron oxide, nitrite, sulfite, silicate, metasilicate, phosphate, polyphosphate, hypophosphate, phosphate, molybdate, phosphomolybdate, borate, metaborate, tungstate, carbonate, and chromate. Examples of inorganic rust inhibitors include phosphate compounds, vanadium compounds, niobium compounds, zirconium compounds, and zinc oxide. Examples of inorganic rust inhibitors include ammonium salts, calcium salts, magnesium salts, aluminum salts, zinc salts, manganese salts, and barium salts.

[0155] Examples of organic rust inhibitors include organic amine compounds, organic amine salts, tannic acid, carboxylic acids, and esters or salts of these acids. Examples of organic rust inhibitors include sulfonates, organic phosphates, benzotriazole compounds, benzothiazole compounds, mercaptan compounds, guanidino group-containing compounds, biguanidino group-containing compounds, thiocarbonyl group-containing compounds, alkylphenol compounds, diisopropylammonium nitride, and dicyclohexylammonium nitride.

[0156] Examples of rust-preventive paints include epoxy resin paints, urethane resin paints, acrylic resin paints, silicone acrylic resin paints, styrene resin paints, fluororesin paints, and zinc-rich paints containing an organic binder and zinc powder. Rust-preventive paints may contain a binder and a rust inhibitor. Examples of binders for rust-preventive paints include organic binders such as epoxy resins, urethane resins, acrylic resins, silicone acrylic resins, styrene resins, and fluororesins. Examples of binders for rust-preventive paints include inorganic binders such as alkyl silicates.

[0157] Epoxy resin paint contains epoxy resin as a binder. Epoxy resin paint has excellent water resistance. Therefore, the rust-preventive function of the rust-preventive layer 18 formed by the epoxy resin paint can be improved. In addition, because epoxy resin paint has excellent adhesion, the rust-preventive layer 18 formed by the epoxy resin paint can adhere closely to the steel material 20.

[0158] From the viewpoint of the rust prevention mechanism, the rust-converting type and the salt / iron ion detoxification type can be classified. The rust-converting layer 18 may be either the rust-converting type or the salt / iron ion detoxification type.

[0159] The rust-preventive paint may be a one-component curing solvent-based paint or a two-component curing solvent-based paint. A solvent-based paint is a paint that contains a solvent. In other words, the rust-preventive paint may be a one-component curing rust-preventive paint or a two-component curing rust-preventive paint containing a main component and a hardener. In the case of a two-component curing rust-preventive paint, the main component containing a binder and optionally a rust inhibitor, and the hardener that promotes the cross-linking reaction may be stored in separate containers and mixed immediately before use. The two-component curing rust-preventive paint is superior in that it has high adhesion to the steel material 20, high coating strength, and can create a dense rust-preventive layer 18. The two-component curing rust-preventive paint also has excellent adhesion to the covering sheet 30. The two-component curing rust-preventive paint may be a two-component curing epoxy resin paint, a two-component curing urethane resin paint, or a two-component curing epoxy resin paint.

[0160] Two-component epoxy resin coatings may contain an epoxy resin as a binder and an epoxy resin curing agent as a curing agent. Examples of curing agents include amine curing agents, phenol curing agents, acid anhydride curing agents, and mercaptan curing agents. Urethane resin coatings may be two-component coatings consisting of a polyol compound and an isocyanate compound, or they may be one-component coatings that cure by moisture in the air.

[0161] Rust-preventive paints may contain moisture-curing resins. Moisture-curing resins have isocyanate groups as reactive groups. The isocyanate groups of moisture-curing resins harden by reacting with water through the reaction shown in formula (I) below. Specifically, first, the isocyanate groups of the moisture-curing resin react with water to produce carbamic acid. Subsequently, the carbamic acid is decomposed to produce an amine. Then, the amine reacts with the isocyanate groups of the moisture-curing resin to form a crosslinking reaction that creates a urea bond. This crosslinking reaction hardens the moisture-curing resin. By containing moisture-curing resins in rust-preventive paints, a rust-preventive effect is obtained by removing water, which can be a corrosive factor.

[0162] [ka]

[0163] For example, the moisture-curing resin contained in rust-preventive paint is urethane resin. In this case, the rust-preventive paint may be a two-component curing type urethane resin paint that neutralizes salt and iron ions.

[0164] When the rust-preventive coating contains a moisture-curing resin, carbon dioxide may be generated when the moisture-curing resin reacts with water, as shown in formula (I) above. As shown in Figure 1A, when the coating sheet 30 and the rust-preventive layer 18 cover the steel material 20, it is preferable that the coating sheet does not have oxygen barrier properties in order to suppress the generation of carbon dioxide remaining in the coating sheet 30 as bubbles instead of passing through it. The coating sheet 30 may also have oxygen permeability. By not having oxygen barrier properties in the coating sheet 30, carbon dioxide can pass through the coating sheet 30 more easily, and the retention of carbon dioxide as bubbles in the coating sheet 30 can be suppressed. Therefore, the coating sheet 30 can adhere closely to the rust-preventive layer 18. In addition, by reducing the retention of bubbles, the transmission haze of the coating sheet 30 decreases and the total light transmittance increases. Therefore, the visibility of the rust-preventive layer 18 and the steel material 20 through the coating sheet 30 is less likely to be obstructed by bubbles. Therefore, when a rust-preventive paint containing a moisture-curing resin is used, it is preferable that the covering sheet 30 does not have oxygen barrier properties.

[0165] Rust-preventive coatings may contain additives. Examples of additives include rosins, plasticizers, extender pigments, coloring pigments, solvents, curing accelerators, coupling agents, corrosive ion immobilizers, anti-sagging agents, and anti-settlement agents. Examples of coupling agents include silane coupling agents, titanium coupling agents, aluminum coupling agents, and zirconium coupling agents. Examples of corrosive ion immobilizers include hydrotalcite and hydrocalmite.

[0166] On the surface of the rust-preventive layer 18 provided on the steel material 20, the 85-degree specular gloss may be 3 or higher. The 85-degree specular gloss on the surface of the rust-preventive layer 18 may be 5 or higher, 10 or higher, 15 or higher, 20 or higher, or 23 or higher. By setting the lower limit of the 85-degree specular gloss on the surface of the rust-preventive layer 18 in this way, the rust-preventive layer 18 becomes a dense film. The rust-preventive layer 18 as a dense film exhibits high adhesion with the covering sheet 30. The upper limit of the 85-degree specular gloss on the surface of the rust-preventive layer 18 is not particularly limited. The 85-degree specular gloss on the surface of the rust-preventive layer 18 may be 60 or less, 50 or less, or 40 or less.

[0167] The specular gloss of the anti-corrosion layer 18 shall be the value measured in accordance with JIS Z8741:1997, except that the incident angle is set to 85°. The measurement environment for measuring the specular gloss of the anti-corrosion layer 18 shall be a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The sample to be measured shall be placed in the measurement environment for 16 hours before the start of measurement. Before measuring the specular gloss, the light source of the measuring device shall be turned on for 15 minutes to stabilize the output of the light source.

[0168] The specular gloss of the anti-corrosion layer 18 shall be the arithmetic mean of five measured values. The five measured values ​​shall be taken at five measurement locations on the measurement sample to be evaluated. The five measurement locations shall be located at least 10 mm apart from each other.

[0169] A lower limit may be set for the maintenance rate of the 85-degree mirror gloss of the rust-preventive layer 18 provided on the steel material 20. By setting a lower limit for the maintenance rate of the 85-degree mirror gloss on the surface of the rust-preventive layer 18, the adhesion of the rust-preventive layer 18 to the steel material 20 can be ensured. The maintenance rate of the 85-degree mirror gloss on the surface of the rust-preventive layer 18 may be 60% or more, 70% or more, 80% or more, 90% or more, or 95% or more.

[0170] The retention rate of 85-degree specular gloss is the retention rate of 85-degree specular gloss on the surface of the rust-preventive layer 18 before and after performing the 90-degree tape peel test. The 85-degree specular gloss on the surface of the rust-preventive layer 18 before performing the 90-degree tape peel test is denoted as "Gsb". The 85-degree specular gloss on the surface of the rust-preventive layer 18 after performing the 90-degree tape peel test is denoted as "Gsa". The retention rate of 85-degree specular gloss is expressed as Gsa × 100 / Gsb, and the unit is %.

[0171] The 90-degree tape peel test is performed as follows: From a roll of 24mm wide cellophane adhesive tape conforming to JIS Z1522:2009, 25cm is unwound in an environment of 23℃±2℃ and 50%±5% relative humidity. With 10cm of adhesive surface to be joined together to create a handle, 5cm of the adhesive surface is attached to the rust-preventive coating surface of a steel structure using a 2kg pressure roller for two passes, and then further attached by finger pressure to ensure no air is trapped. Next, the cellophane adhesive tape is peeled off once manually at a speed of 5cm / s in a 90-degree direction from the rust-preventive coating surface. As the cellophane adhesive tape used, Cellotape (registered trademark) (manufactured by Nichiban, model No. 405-1P, 24mm wide) is used. If this product cannot be used, a 24mm wide cellophane adhesive tape conforming to JIS Z1522:2009 with equivalent adhesive strength is used.

[0172] <<Top coat layer>> The topcoat layer 19 shown in Figure 1A is formed on the covering sheet 30. In this example, the covering sheet 30 is located between the topcoat layer 19 and the steel material 20 in the lamination direction. The topcoat layer 19 may be provided for the purpose of improving the weather resistance of the steel structure 10. The topcoat layer 19 may provide the steel structure 10 with excellent rust prevention over a long period of time. The topcoat layer 19 may be a colored paint. The topcoat layer 19 can be omitted from the steel structure 10.

[0173] The topcoat layer 19 may be prepared by applying a topcoat paint to the first surface 31 of the covering sheet 30 to form a coating film, and then drying and solidifying or hardening this coating film. Examples of painting methods include brush painting, roller painting, and spray painting (e.g., air spray, airless spray). The topcoat paint may be a one-component paint or a two-component paint. The topcoat layer 19 and the topcoat paint may contain resins and additives.

[0174] Examples of topcoat paints include urethane resin paints, fluororesin paints, acrylic resin paints, butadiene resin paints, silicone resin paints, vinyl ester resin paints, and epoxy resin paints. Examples of binders for topcoat paints include urethane resins, fluororesins, acrylic resins, butadiene resins, silicone resins, vinyl ester resins, and epoxy resins. Examples of fluororesins include polyvinyl fluoride, polytetrafluoroethylene, perfluoroalkoxyalkanes, and ethylene-tetrafluoroethylene copolymers. Examples of additives contained in the topcoat layer 19 and the topcoat paint include pigments, dyes, dispersants, defoamers, thickeners, leveling agents, anti-settling agents, anti-sagging agents, anti-algal agents, anti-fungal agents, preservatives, UV absorbers, antioxidants, and light stabilizers.

[0175] Urethane resin paint contains urethane resin. Examples of urethane resin paint include polyurethane resin paint and acrylic urethane resin paint. Urethane resin paint has gloss and excellent appearance. Therefore, the appearance of a steel structure 10 including a topcoat layer 45 formed with urethane resin paint can be improved.

[0176] Fluoropolymer paint contains fluoropolymer. Fluoropolymer paint has excellent weather resistance. Therefore, the topcoat layer 45 formed by the fluoropolymer paint can protect the steel material 20 for a long period of time.

[0177] The topcoat paint may contain organic solvents and / or water for purposes such as adjusting viscosity. Examples of organic solvents include aromatic hydrocarbons, aliphatic hydrocarbons, ketones, acetate esters, ethers, alcohol solvents, and mineral spirits.

[0178] The thickness of the topcoat layer 19 may be 5 μm or more, 10 μm or more, or 15 μm or more. The thickness of the topcoat layer 19 may be 200 μm or less, 150 μm or less, or 100 μm or less.

[0179] <<Multiple coatings>> The multiple coatings 15 included in the steel structure 10 shown in Figure 1B include, in this order: a rust-preventive layer 41, a first undercoat layer 42, a second undercoat layer 43, an intermediate coat layer 44, and a topcoat layer 45.

[0180] The rust-preventive layer 41 has a rust-preventive function. The rust-preventive layer 41 is a layer that suppresses rust formation and rust spread. The rust-preventive layer 41 may be configured in the same way as the rust-preventive layer 18 described above.

[0181] The first undercoat layer 42 and the second undercoat layer 43 have gas barrier properties. The first undercoat layer 42 and the second undercoat layer 43 suppress corrosion of the steel material 20. The barrier properties of the coating film barrier layer are weaker than those of the vapor-deposited film barrier layer. In the steel structure 10 shown in Figure 1B, two undercoat layers 42 and 43 are included to ensure sufficient barrier properties. The undercoat layers 42 and 43 may contain epoxy resin. The undercoat layers 42 and 43 may contain cured products of curable resin.

[0182] The intermediate coat layer 44 has good adhesion properties. The intermediate coat layer 44 improves the adhesion of the top coat layer 45. An example of an intermediate coat layer with good adhesion properties is a layer containing fluororesin. The intermediate coat layer 44 may also contain weather-resistant agents such as UV absorbers, antioxidants, and light stabilizers.

[0183] The topcoat layer 45 is weather-resistant. The topcoat layer 45 is made by applying a topcoat paint to the intermediate coat layer 44 to form a coating film, which is then dried and solidified or cured. The topcoat layer 45 contains weather-resistant agents such as ultraviolet absorbers, antioxidants, and light stabilizers. The topcoat layer 45 may be configured in the same way as the topcoat layer 19 described above. That is, examples of topcoat paints that form the topcoat layer 45 include urethane resin paint, fluororesin paint, acrylic resin paint, butadiene resin paint, silicone resin paint, vinyl ester resin paint, and epoxy resin paint. A covering sheet 30 is attached to the topcoat layer 45. By laminating the topcoat layer 45 and the covering sheet 30 onto the steel material 20, the durability of the steel structure 10 can be improved.

[0184] Urethane resin paint contains urethane resin. Examples of urethane resin paint include polyurethane resin paint and acrylic urethane resin paint. Urethane resin paint has gloss and excellent appearance. Therefore, the appearance of a steel structure 10 including a topcoat layer 45 formed with urethane resin paint can be improved.

[0185] Fluoropolymer paint contains fluoropolymer. Fluoropolymer paint has excellent weather resistance. Therefore, the topcoat layer 45 formed by the fluoropolymer paint can protect the steel material 20 for a long period of time.

[0186] Next, a method for repairing steel structures using the covering sheet 30 will be explained.

[0187] The steel structure to be repaired may, for example, be a steel structure 10 including a covering sheet 30 as shown in Figure 1A. As another example shown in Figure 5, the steel structure to be repaired may be a steel structure 100 including a steel material 20 and a plurality of coating films 50 formed on the steel material 20.

[0188] Figure 5 shows a steel structure 100 to be repaired, which includes numerous coatings 50. The coatings 50 included in the steel structure 100 include, in order from the steel material 20, a rust-preventive layer 51, a first undercoat layer 52, a second undercoat layer 53, an intermediate coat layer 54, and a topcoat layer 55. The numerous coatings 50 may be configured in the same way as the numerous coatings 15 included in the steel structure 10 shown in Figure 1B. That is, the rust-preventive layer 51, the first undercoat layer 52, the second undercoat layer 53, the intermediate coat layer 54, and the topcoat layer 55 included in the numerous coatings 50 may be configured in the same way as the rust-preventive layer 41, the first undercoat layer 42, the second undercoat layer 43, the intermediate coat layer 44, and the topcoat layer 45, respectively.

[0189] Each of the numerous coating films 50 is prepared only once a day, taking into account the time required for drying, solidification, and curing. For example, the steel structure 100 shown in Figure 5 requires 5 days of construction.

[0190] Referring to Figures 4A to 4D, the repair method for the steel structure 100 shown in Figure 5 will be explained. A covering sheet 30 is used for the repair. The repaired steel structure 10 includes the covering sheet 30. The method is not limited to the examples shown in Figures 4A to 4D; a steel structure 10 including the covering sheet 30 may also be repaired using the covering sheet 30.

[0191] The repair method according to this embodiment includes the steps of surface preparation, forming a coating film, drying the coating film, and joining a covering sheet to the coating film. In the surface preparation step, surface preparation is performed on the deteriorated part 12 of the steel structure 100. In the coating film formation step, paint is applied to the steel material 20 to form a coating film 15. In the coating film drying step, the coating film 15 is dried. In the joining of the covering sheet to the coating film step, the covering sheet 30 is joined to the coating film 15 using the joining layer 35 contained in the covering sheet 30. The repair method may also include the step of preparing the covering sheet 30. The step of preparing the covering sheet 30 is performed before the step of joining the covering sheet 30. The step of preparing the covering sheet 30 may be performed in parallel with one or more of the steps of surface preparation, forming a coating film, and drying the coating film. Hereinafter, each step of the repair method according to this embodiment will be described in order with reference to Figures 4A to 4B.

[0192] Figure 4A schematically shows the steel structure to be repaired in the following explanation, along with its deteriorated portion 12. In Figure 4A, a pre-repair coating (old coating) 50 is applied to the steel material 20. Rust 21 has formed on the steel material 20.

[0193] Figure 4B is a diagram illustrating the process of surface preparation. As shown in Figure 4B, in the surface preparation process, surface preparation (undercoat preparation) is performed on the deteriorated part 12 of the steel structure 100. Surface preparation is exemplified as a method for preparing the surface of the steel structure 100. In surface preparation, the old paint film 50, rust 21, dust, and dirt are generally removed by blasting, power tools, or manual tools. This removal exposes the surface preparation surface 22. In the surface preparation process, the surface preparation surface 22 constitutes the surface of the steel structure 100.

[0194] Surface preparation processes are categorized into four grades: Grade 1, Grade 2, Grade 3, and Grade 4. The lower the grade number, the more advanced the level of surface preparation.

[0195] "Type 1 surface preparation" refers to surface preparation that involves removing all rust 21 and old paint film 50 to expose the surface of the steel material. In "Type 1 surface preparation," surface preparation is mainly performed by blast treatment.

[0196] "Type 2 surface preparation" refers to surface preparation that removes rust and old paint film 50 to expose the surface of the steel material 20. In "Type 2 surface preparation," surface preparation is mainly carried out using power tools and / or manual tools.

[0197] "Type 3 surface preparation" refers to a surface preparation process that leaves the healthy paint film 50P (i.e., paint film in good condition) while removing other defective parts (rust 21 and dead paint film (paint film with cracks and blistering)) from the old paint film 50. In "Type 3 surface preparation," surface preparation is mainly carried out using power tools and / or manual tools.

[0198] Type 3 surface preparation has the advantage of requiring fewer work areas and lower labor costs compared to Type 1 and Type 2 surface preparation. Since the active film 50P of the old paint film 50 remains, the surface prepared after Type 3 surface preparation may have large irregularities. Rust may remain on the surface prepared after Type 3 surface preparation. The height of the irregularities on the surface of the steel structure 10 after Type 3 surface preparation may be 10 μm or more and 1000 μm or less, 30 μm or more and 500 μm or less, or 50 μm or more and 300 μm or less.

[0199] Figure 4B shows a steel structure 100 that has undergone surface preparation using three types of surface preparation. In Figure 4B, the old paint film 50 has been removed except for the active film 50P. In Figure 4B, the rust 21 has also been removed.

[0200] "Type 4 surface preparation" refers to surface preparation that removes powdery substances (including loose rust) and dirt adhering to the surface. In "Type 4 surface preparation," surface preparation is mainly carried out using manual tools and / or brushes.

[0201] Examples of power tools include disc sanders and wire wheels. Examples of hand tools include wire brushes, scrapers, scraping rods, and sandpaper.

[0202] In the process of forming the coating film, as shown in Figure 4C, a coating film 15 is formed on the steel structure 100 by applying paint to the steel structure 100. As mentioned above, examples of coating films 15 include a rust-preventive layer 18 and a topcoat layer 45.

[0203] If the coating 15 is a rust-preventive layer 18, rust-preventive treatment is performed on the surface preparation surface 22. That is, the rust-preventive layer 18 is formed on the steel material 20 and the active film 50P by the process of forming the coating. The material and formation method of the rust-preventive layer 18 are as described above.

[0204] The rust-preventive layer 18 contains a rust inhibitor. The rust inhibitor can suppress rust formation. By providing the rust-preventive layer 18 containing the rust inhibitor separately from the coating sheet 30, the effect of the rust inhibitor can be more clearly obtained. The rust-preventive layer 18, formed as a coating film 15, can fill in the irregularities of the surface preparation to some extent. This flattening improves the adhesion of the coating sheet 30.

[0205] If the coating film 15 is a topcoat layer 45, a large number of coating films 15 may be formed on the steel material 20 and the active film 50P during the coating film formation process.

[0206] A step of applying unevenness putty may be performed before the step of forming the coating film. In the step of applying unevenness putty, the unevenness putty may be applied to the uneven parts of the surface preparation surface to flatten the surface. The coating film 15 may be formed after the step of applying unevenness putty. That is, an unevenness putty layer may be formed beneath the coating film 15. By providing an unevenness putty layer, the surface to which the covering sheet 30 is joined is flattened. Therefore, the adhesion of the covering sheet 30 to the steel structure 10 can be improved.

[0207] Examples of materials that make up the unevenness putty layer include fluororesin, acrylic resin, silicone resin, urethane resin, urea resin, and epoxy resin. The unevenness putty layer may also be made by forming a coating film by applying paint and then solidifying or curing this coating film. The paint may be a one-component curing type or a two-component curing type. The unevenness putty layer may contain additives such as ultraviolet absorbers, antioxidants, and light stabilizers.

[0208] Next, a process for drying the coating is carried out. In the coating drying process, the coating on the steel structure 100 is dried. In the coating drying process, the coating may be allowed to air dry by leaving it unattended. In the coating drying process, heated air may be blown onto the coating. In the coating drying process, the coating may be hardened while drying. In the coating hardening process, drying and solidification or hardening may be carried out in parallel by heating the coating.

[0209] Conventionally, when applying a coating paint to a coating film, it was considered preferable to allow the underlying coating film to dry for about 24 hours. In other words, the paint to be applied to form the next coating film was applied to the underlying coating film only after it had been sufficiently dried and solidified. It was believed that if the underlying coating film was not sufficiently solidified, the components of the underlying coating film and the components of the paint would mix, resulting in insufficient adhesion between the underlying coating film and the next coating film to be formed. It was also believed that the underlying coating film needed to be sufficiently dried and solidified when attaching a covering sheet containing a bonding layer to the underlying coating film. There were concerns that the solvents contained in the underlying coating film would damage the bonding layer of the covering sheet.

[0210] In the steel structure repair method and the marker manufacturing method described later according to this embodiment, the drying of the coating film 15 in the coating film drying step is carried out until the tack T of the coating film 15 becomes 2.0 N / φ5 mm or less. In other words, it is not necessary to wait for the coating film 15 to dry until its tackiness disappears. The inventors have confirmed that by reducing the tack T of the coating film 15 to 2.0 N / φ5 mm or less, sufficient adhesion between the coating film 15 and the covering sheet 30 can be ensured. By setting an upper limit for tack T, it is sufficient to ensure the minimum drying time required for the formation of the coating film 15. Therefore, by proceeding to the next step when the tack T falls below the upper limit, the process time can be shortened while drying the coating film 15 to the required extent. Shorter drying time also shortens the overall construction time of the steel structure 10.

[0211] In the drying process of the coating film, the coating film 15 may be dried so that its tack T is between 0.38 N / φ5 mm and 2.0 N / φ5 mm. The inventors confirmed that if the underlying coating film is dried too much, the adhesion after the weathering test tends to decrease. By ending the drying process before the underlying coating film is completely dried and the coating film 15 is completely solidified or hardened, and then laminating the covering sheet 30 to the coating film 15, the decrease in peel strength after the weathering test could be suppressed. Therefore, by setting not only an upper limit but also a lower limit for the tack of the coating film 15 after the drying process, the covering sheet 30 can protect the steel material 20 for a long period of time.

[0212] Furthermore, the inventors confirmed that, with a low probability, if the base coating film was dried too much, the adhesion between the base coating film and the covering sheet decreased somewhat. By ending the drying process before the base coating film is completely dry and the coating film 15 is completely solidified or cured, and then bonding the covering sheet 30 to the coating film 15, excellent adhesion between the coating film and the covering sheet can be stably ensured.

[0213] Tack T is measured by the probe tack test method. The probe tack test method is a test method in which a probe is pressed vertically onto the coating film, and the resistance force when the probe is removed from the coating film is obtained as tack. Tack is measured using a tacking test machine 60 as shown in Figure 6.

[0214] The tacking test machine 60 includes a table 61 and a probe 65. The table 61 is positioned so that its top surface is horizontal. The probe 65 is formed in a cylindrical shape with a diameter of 5 mm. The probe 65 is positioned above the table 61. The axial direction of the probe 65 is perpendicular to the top surface of the table 61. During testing, the axial direction of the probe 65 is parallel to the vertical direction. The probe 65 is movable relative to the table 61 in the axial direction. The probe 65 can move axially to approach and away from the table 61 on which the sample is placed.

[0215] The test specimen 70 includes a plate-shaped steel material 71 and a coating film 72. The coating film 72 is formed by applying paint 73 to the plate surface of the steel material 71. The coating film 72 constitutes one side of the test specimen 70.

[0216] The specific measurement method will now be explained. First, the test specimen 70 is fixed to the upper surface of the table 61 so that the coating 72 faces upward. The test specimen 70 is fixed to the table 61 so that it is positioned directly below the probe 65 in the vertical direction. The probe 65 is moved downward at a speed of 30 mm / min, approaching the coating 72. Once the tip of the probe 65 makes contact with the coating 72, the coating is pressed with a load of 25 gf for 1 second. Next, the probe 65 is moved upward at a speed of 30 mm / min, detaching the probe 65 from the coating 72. As the probe 65 is detached from the coating, the probe 65 experiences resistance due to the adhesive force of the coating. That is, the probe 65 receives a downward force that hinders its upward movement due to the adhesion between the probe 65 and the coating 72. This resistance force (N) experienced by the probe 65 during its movement is measured. The maximum resistance applied to probe 65 is taken as the measured value of the tack T(N) of the test subject. The contact surface of probe 65 with the coating is a circle with a diameter of 5 mm.

[0217] For the sample to be evaluated, the tack will be measured at three measurement points. The arithmetic mean of the three tack measurements taken at the three measurement points will be used as the tack for evaluation. The three measurement points will be at least 10 mm apart from each other. Each measurement point will be at least 10 mm away from the edge of the coating film on the evaluation sample.

[0218] The process of drying the coating film may include a step of evaluating the tack of the coating film. In the step of evaluating the tack of the coating film, the tack of the coating film is actually measured. In the step of evaluating the tack of the coating film, it may be confirmed that the measured tack of the coating film is 2.0 N / φ5 mm or less. If the measured tack of the coating film is greater than 2.0 N / φ5 mm, the drying process of the coating film may be continued. Alternatively, after continuing the drying process of the coating film, the tack of the coating film may be measured again. The measurement of tack and drying may be repeated until the tack of the coating film is 2.0 N / φ5 mm or less.

[0219] In the process of evaluating the tack of the coating on the steel structure 10, it is difficult to measure the tack of the coating on the actual steel structure 10 during its construction. Therefore, in the process of evaluating the tack of the coating, instead of measuring the coating on the actual steel structure 10 during its construction, the coating on a test sample is measured. The test sample is made using SS400 (surface roughness Rz25μm in accordance with JIS C3101 and JIS B0601:2013), a common structural rolled steel, as the steel material. The thickness of the SS400 plate is 3.2 mm. A coating with the same composition (same material, same thickness, etc.) as the coating formed on the actual steel structure 10 is formed on the SS400 plate. The formation of the coating on the test sample is carried out in parallel with the formation of the coating on the actual steel structure 10. The formation of the coating on the test sample is carried out in the same environment as the formation of the coating on the actual steel structure 10.

[0220] The drying time of the coating film 15 may be set to 2 hours or more. In paints and coating films applied to general steel structures 10, including bridges, bridge piers, steel towers, steel pipes, chimneys, tanks, plants, pipelines, rolled plates, and roofs as described above, the tack of the coating film will be 2.0 N / φ5 mm or less after 2 hours of natural drying. Therefore, by drying the coating film for 2 hours or more, sufficient adhesion between the coating film 15 and the covering sheet 30 can be ensured. By setting a lower limit for the drying time, the process time can be shortened while ensuring sufficient drying. Shorter drying times also shorten the overall construction time for the steel structure 10.

[0221] The drying time for the coating film 15 may be less than 24 hours, 12 hours or less, 10 hours or less, 8 hours or less, or 4 hours or less. As described above, by ending the drying process and laminating the coating sheet 30 to the coating film 15 before the underlying coating film is completely dry and the coating film 15 is completely solidified or hardened, the decrease in peel strength after the weathering test can be suppressed. By setting not only a lower limit but also an upper limit for the time during which the drying process is carried out, the coating sheet 30 can protect the steel material 20 for a long period of time.

[0222] Furthermore, as mentioned above, if the underlying coating is allowed to dry too much, the adhesion between the underlying coating and the covering sheet may decrease somewhat. By setting an upper limit on the drying time, the drying process can be terminated before the underlying coating is completely dry and the coating 15 is completely solidified or cured. Therefore, by setting an upper limit on the drying time, excellent adhesion between the coating and the covering sheet can be stably ensured.

[0223] In the process of joining the covering sheet to the coating film, the steel material 20 of the surface-prepared steel structure 100 is covered with the covering sheet 30. In the process of joining the covering sheet to the coating film, the covering sheet 30 is placed on the steel structure 100 under repair. As a result, the steel material 20 is covered with the covering sheet 30. In the example shown in Figure 4D, the covering sheet 30 is placed on the coating film 15. The covering sheet 30 is joined to the coating film 15 using a bonding layer 35. By joining the covering sheet to the coating film, a steel structure 10 including the covering sheet 30 is obtained.

[0224] The covering sheet 30 may be attached to the steel structure 10 by the bonding layer 35 while being pressurized at room temperature. For example, the covering sheet 30 may be pressed toward the steel material 20 using a roller or the like from above. This allows the covering sheet 30 and the coating film 15 to adhere tightly to each other.

[0225] If the covering sheet 30 includes a release film 38, the release film 38 is peeled off the covering sheet 30 before placing the covering sheet 30 on the steel material 20. By peeling off the release film 38, the bonding layer 35 is exposed.

[0226] The covering sheet 30 may cover the side edges of the coating film 15. The covering sheet 30 may be folded to cover the side end surfaces of the steel structure 10.

[0227] As described above, the steel structure is repaired using the covering sheet 30, and a steel structure 10 including the covering sheet 30 is obtained. Repair using the covering sheet 30 allows the steel structure 100 to be repaired in a short period of time. For example, compared to reforming a large number of coatings 50 at the repair site as shown in Figure 5, the construction period can be significantly shortened by using the covering sheet 30 instead of the large number of coatings 50. In addition, repair using the covering sheet 30 can reduce costs and simplify construction.

[0228] The method for repairing steel structures using the covering sheet 30 is not limited to the method described above with reference to Figures 4A to 4D.

[0229] In the illustrated example, Type 3 surface preparation is performed as part of the surface preparation process. However, the repair method using the covering sheet 30 is not limited to this example. The repair method using the covering sheet 30 can be applied to steel structures where Type 1, Type 2, or Type 4 surface preparation is performed as part of the surface preparation, in addition to Type 3 surface preparation.

[0230] The repair method described above may include a step of preparing the topcoat layer 19.

[0231] As already mentioned, the steel structure 10 including the covering sheet 30 may be repaired using the covering sheet 30, and is not limited to the examples shown in Figures 4A to 4D. In this example, the covering sheet 30 that was previously used may be removed from the steel structure 10 during the surface preparation process.

[0232] Next, a method for manufacturing a steel structure 10 using a covering sheet 30 will be described.

[0233] The manufacturing method comprises the steps of applying paint to the steel material 20 to form a coating film 15, drying the coating film 15, and joining the coating sheet 30 to the coating film 15 using the bonding layer 35 contained in the coating sheet 30. The manufacturing method differs from the steel structure repair method described above in that it does not include a step of surface preparation for deteriorated parts of the steel structure 100, but is otherwise identical to the steel structure repair method described above. The steel material 20 that will be used as the material for the steel structure 10 does not need to contain deteriorated parts. In other words, the steel material 20 does not need to contain rust 21. To put it another way, the steel material 20 can be new. The manufacturing method for the steel structure 10 will be described below in order.

[0234] The method for manufacturing the steel structure may include a step of preparing the covering sheet 30, similar to the method for repairing the steel structure described above.

[0235] In the process of forming a coating film in the manufacturing method of a steel structure, a coating film 15 is formed on the steel material 20. The coating film 15 is formed by applying paint to the steel material 20 and drying it to solidify or harden it. As mentioned above, examples of the coating film 15 include a rust-preventive layer 18 and a topcoat layer 45. The process of forming a coating film in the manufacturing method of a steel structure may be the same as the process of forming a coating film in the steel structure repair method described above.

[0236] In the process of forming a coating film in the manufacturing method of a steel structure, the coating film is dried until its tack is 2.0 N / φ5 mm or less. Alternatively, in the process of forming a coating film in the manufacturing method of a steel structure, the coating film may be dried until its tack is 0.38 N / φ5 mm or more and 2.0 N / φ5 mm or less.

[0237] Alternatively, in the process of forming a coating film in the manufacturing method of a steel structure, the coating film may be dried for two hours or more. In the process of forming a coating film in the manufacturing method of a steel structure, the coating film may be dried for two hours or more but less than 24 hours.

[0238] The step of drying the coating in the method for manufacturing steel structures may be the same as the step of drying the coating in the method for repairing steel structures described above.

[0239] In the step of joining the covering sheet 30 to the coating film, the steel material 20 is covered with the covering sheet 30. The covering sheet 30 is attached to the coating film 15 using a bonding layer 35. By joining the covering sheet 30 to the coating film, a steel structure 10 including the covering sheet 30 is obtained. The step of joining the covering sheet 30 to the coating film in the manufacturing method of the steel structure may be the same as the step of joining the covering sheet to the coating film in the steel structure repair method described above.

[0240] As a result, a steel structure 10 including the covering sheet 30 is obtained. According to the method for manufacturing a steel structure using the covering sheet 30, a steel structure can be manufactured in a short period of time.

[0241] The above-described manufacturing method may include a step of producing the topcoat layer 19. [Examples]

[0242] This disclosure will be further described in detail by examples. This disclosure is not limited to the following examples.

[0243] <<<1. Fabrication of Steel Structures>>> Steel structures according to Example 1, Example 2, and Comparative Example 1 were fabricated.

[0244] <<Example 1>> As the steel structure according to Example 1, a steel structure was fabricated that included steel material, a rust-preventive layer, and a covering sheet in that order.

[0245] First, a sheet was prepared as a covering sheet, containing, in this order, a release film, a bonding layer, a barrier layer, a second bonding layer, a substrate, a primer layer, and a weather-resistant layer.

[0246] The base material was obtained by forming a resin composition into a sheet. The resin composition was obtained by mixing 95 parts by mass of base resin with 5 parts by mass of a weather-resistant masterbatch.

[0247] The base resin was a metallocene linear low-density polyethylene resin (M-LLDPE). The density of the base resin was 0.901 g / cm3. The melting point of the base resin was 93 °C. The MFR (melt flow rate) of the base resin at 190 °C was 2.0 g / 10 min.

[0248] The weather-resistant masterbatch was obtained by mixing 100 parts by mass of a low-density polyethylene resin, 0.6 parts by mass of HALS, 3.5 parts by mass of a first ultraviolet absorber, and 0.6 parts by mass of a second ultraviolet absorber. The density of the low-density polyethylene resin was 0.880 g / cm3. The MFR (melt flow rate) of the low-density polyethylene resin at 190 °C was 3.5 g / 10 min. The HALS was "KEMISTAB62" manufactured by Chemipro Kasei Co., Ltd. The first ultraviolet absorber was "KEMISORB12" manufactured by Chemipro Kasei Co., Ltd. The second ultraviolet absorber was "KEMISORB79" manufactured by Chemipro Kasei Co., Ltd.

[0249] For sheet formation of the resin composition, a φ30 mm extruder and a film forming machine having a 200 mm wide T-die were used. In the extrusion process by the extruder, the extrusion temperature was 210 °C. The take-up speed of the extruded sheet was adjusted so that the thickness of the base material to be produced was 300 μm. The cooling roll directly below the T-die was chrome-plated. The surface roughness Rz of the cooling roll was 1.5 μm. A silicone rubber roll was used as the rubber roll directly below the T-die. The hardness of the silicone rubber roll was 70 degrees.

[0250] As described above, a transparent base material with a thickness of 300 μm and not colored directly was obtained.

[0251] Next, one surface of the base material was subjected to corona discharge treatment. Then, a primer layer was formed on the corona discharge-treated surface of the base material using the primer layer resin composition.

[0252] The resin composition for the primer layer was prepared by mixing 100 parts by mass of a mixture, 5 parts by mass of a curing agent, 20 parts by mass of an ultraviolet absorber, and a diluting solvent. The 100 parts by mass of the mixture was a mixture composed of a polycarbonate-based urethane-acrylic copolymer and an acrylic polyol. The 5 parts by mass of the curing agent was hexamethylene diisocyanate.

[0253] The resin composition for the primer layer was applied by a gravure printing method onto the treated surface of the base material that had been subjected to corona discharge treatment. The primer layer was obtained by drying the coating film of the resin composition for the primer layer formed on the base material. The thickness of the primer layer was 4 μm.

[0254] Next, a weather-resistant layer was formed on the primer layer using an ionizing radiation curable resin composition. The ionizing radiation curable resin composition was prepared by mixing 100 parts by mass of a urethane acrylate oligomer, 4 parts of a hydroxyphenyltriazine-based ultraviolet absorber as an ultraviolet absorber, and 3 parts by mass of a hindered amine-based non-reactive light stabilizer. The prepared ionizing radiation curable resin composition was applied onto the primer layer to form an uncured resin layer on the primer layer.

[0255] Thereafter, the uncured resin layer was cured by irradiating the uncured resin layer with an electron beam. As the irradiation conditions of the electron beam, the acceleration voltage was 165 kV and the irradiation dose was 5 Mrad (50 kGy). By irradiating the uncured resin layer with the electron beam, a weather-resistant layer with a thickness of 5 μm was formed. The weather-resistant layer and the base material were joined via a primer layer not shown in FIG. 2B.

[0256] Next, a transparent urethane resin adhesive was applied onto the surface of the base material opposite to the surface on which the primer layer and the weather-resistant layer were laminated. The coating film of the urethane resin adhesive was dried on the base material to form a second bonding layer with a thickness of 3 μm.

[0257] Next, IB-PET-PXB2, available from Dai Nippon Printing Co., Ltd., was prepared as a gas barrier film containing a barrier layer. IB-PET-PXB2 contained a resin film and a vapor-deposited gas barrier layer. The substrate and the gas barrier film were bonded by dry lamination using the second bonding layer described above. The gas barrier layer of the gas barrier film was made to contact and bond with the second bonding layer.

[0258] Next, a bonding layer was formed on the side of the gas barrier film opposite to the side bonded to the second bonding layer using an acrylic adhesive. The acrylic adhesive was prepared by mixing 1717DT (main component) and L-45 (curing agent) manufactured by Soken Chemical Co., Ltd. in a ratio of 1.56 parts by weight of curing agent to 100 parts by weight of main component. As a release film, NS Separator, part number MBA38μm, available from Nakamoto Pax Co., Ltd., was prepared. The acrylic adhesive was placed on the release film using a comma coat, and after drying, it was bonded to the gas barrier film to produce a coated sheet including the bonding layer and release film. The thickness of the bonding layer was set to 80μm.

[0259] As a result, a coated sheet was obtained comprising a release film, bonding layer, barrier layer, second bonding layer, substrate, primer layer, and weather-resistant layer in this order.

[0260] We prepared SS400 sheet metal, a common structural rolled steel material. The thickness of the SS400 sheet metal was set to 3.2 mm.

[0261] A rust-preventive layer was formed by applying rust-preventive paint to steel materials with a brush and drying it at room temperature for a predetermined time. The rust-preventive paint used was "Hypon Sabista," available from Nippon Paint Co., Ltd. Six different drying times were used: 0 hours, 0.5 hours, 2 hours, 3 hours, 4 hours, and 24 hours. A different rust-preventive layer was created for each drying time.

[0262] The release film was removed from the coating sheet, and the coating sheet was laminated onto the rust-preventive layer after drying at each drying time. The bonding layer of the coating sheet was brought into contact with the rust-preventive layer. The coating sheet was pressed onto the rust-preventive layer with a roller.

[0263] Based on the above, a steel structure according to Example 1 was obtained, comprising steel material, a rust-preventive layer, and a covering sheet in this order.

[0264] <<Example 2>> As the steel structure according to Example 2, a steel structure was fabricated that included steel material, a topcoat layer, and a covering sheet in that order. Example 2 differed from Example 1 in that the topcoat layer, rather than the rust-preventive layer, was located between the steel material and the covering sheet, but was otherwise identical to Example 1. That is, the steel material and covering sheet in Example 2 were the same as the steel material and covering sheet in Example 1, respectively. The method for forming the topcoat layer and the method for attaching the covering sheet are as follows.

[0265] A topcoat layer was formed by applying the topcoat paint to the steel material with a brush and drying it at room temperature for a predetermined time. "Hypon 50," available from Nippon Paint Co., Ltd., was used as the topcoat paint. The drying times were set to six different values: 0 hours, 0.5 hours, 2 hours, 3 hours, 4 hours, and 24 hours, similar to the drying times for the rust-preventive paint in Example 1. A different rust-preventive layer was prepared for each drying time.

[0266] The release film was removed from the coating sheet, and the coating sheet was laminated onto the topcoat layer after drying at each drying time. The bonding layer of the coating sheet was brought into contact with the topcoat layer. The coating sheet was pressed onto the topcoat layer with a roller, thereby adhering it to the topcoat layer.

[0267] Based on the above, a steel structure according to Example 2 was obtained, comprising steel material, a topcoat layer, and a covering sheet in this order.

[0268] <<Comparative Example 1>> As the steel structure for Comparative Example 1, a steel structure was fabricated containing steel material, a rust-preventive layer, and a primer layer in that order. Comparative Example 1 differed from Example 1 in that the primer layer, rather than a covering sheet, was bonded to the rust-preventive layer, but was otherwise identical to Example 1. That is, the steel material and rust-preventive layer in Comparative Example 1 were the same as the steel material and rust-preventive layer in Example 1, respectively. The method for forming the rust-preventive layer and the primer layer is as follows.

[0269] The rust preventive layer was formed in the same manner as in Example 1. The drying times were six types: 0 hour, 0.5 hour, 2 hours, 3 hours, 4 hours, and 24 hours. Different rust preventive layers were produced for each drying time.

[0270] The undercoat paint was applied to the rust preventive layer after drying at each drying time with a brush and dried at room temperature for 16 (numerical value) hours to form an undercoat layer. "Hypon 20 Fine" available from Nippon Paint Co., Ltd. was used as the undercoat paint.

[0271] As described above, a steel structure according to Comparative Example 1 including a steel material, a rust preventive layer, and an undercoat layer in this order was obtained.

[0272] <<<2. Measurement and Evaluation>>> Next, as described below, the steel structures according to the examples and comparative examples were measured and evaluated. The test environment for the measurement and evaluation was a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. Before starting the measurement and evaluation, the target samples were placed in the above test environment for 16 hours. Also, it was visually confirmed that there were no abnormalities such as dust or scratches on the samples used for the measurement and evaluation. The measurement and evaluation results of Example 1, Example 2, and Comparative Example 1 are shown in Table 1, Table 2, and Table 3, respectively.

[0273] <<2-1. Appearance Evaluation>> The steel structures according to the examples and comparative examples were observed and the appearance was evaluated. Specifically, the presence or absence of lifting or peeling of the coating sheet was evaluated. The evaluation results are shown in "Appearance" in Tables 1 to 3. The evaluation criteria were as follows. AA: There was no lifting or peeling. A: When observed carefully, very slight lifting or peeling was present, but there were no problems with adhesion or visibility, etc. B: Lifting or peeling was present.

[0274] <<2-2. Peeling Strength Immediately after Coating>> The peel strength of the coating sheet immediately after fabrication of the steel structure for each example was measured using the method described above. For Example 1 and Example 2, the peel strength test was performed after the coating sheet had been bonded to the coating film and left for at least 24 hours. The results of the peel strength measurement are shown in the "Initial Peel Strength" column of Tables 1 and 2.

[0275] The failure state of samples that fractured in the peel strength test was investigated. Specifically, the failure state was investigated to determine whether it was cohesive failure, where the fracture occurred inside the bonding layer of the coating sheet, or interfacial failure, where the bonding layer peeled off from the coating at the interface between the coating and the bonding layer. The investigation results are shown in the "Failure State" column of Tables 1 and 2. For cases where interfacial failure occurred throughout the entire area, "AF" was entered in the "Failure State" column of Tables 1 and 2. For cases where cohesive failure occurred throughout the entire area, "CF" was entered in the "Failure State" column of Tables 1 and 2. For cases where interfacial failure occurred in X% of the area based on visual inspection, and cohesive failure occurred in the remaining Y% of the area, "AFXCFY" was entered in the "Failure State" column of Tables 1 and 2. For example, in the case where "CF30AF70" was entered, cohesive failure occurred in 30% of the area and interfacial failure occurred in 70% of the area.

[0276] <<2-3. Peel strength after weathering test>> 3cm x 3cm samples were cut from the steel structures of Example 1, where the coating film drying time was 2 hours and 24 hours, and from the steel structures of Example 2, where the coating film drying time was 2 hours and 24 hours. Weathering tests were performed on the samples from each example. The weathering tests were conducted under the following conditions.

[0277] The sample was exposed to the irradiation and condensation processes for a total of over 120 hours, with five cycles consisting of a 20-hour irradiation process and a 4-hour condensation process. A 30-second shower process was performed after the irradiation process and before the condensation process, and after the condensation process and before the irradiation process. In the shower process, the evaluation sample held in the weather resistance testing apparatus was subjected to a shower of water.

[0278] As the weather resistance testing equipment, the "i-Super UV Tester SUV-W261" ultra-accelerated weather resistance testing equipment manufactured by Iwasaki Electric Co., Ltd. was used. The UV lamp, lamp jacket, and illuminance meter included in the weather resistance testing equipment were as follows: • UV lamp: Product name: M04-L21WB / SUV, manufactured by Iwasaki Electric Co., Ltd. • Lamp jacket: Product name: WJ50-SUV, manufactured by Iwasaki Electric Co., Ltd. • Illuminance meter: Product name: UVD-365PD, manufactured by Iwasaki Electric Co., Ltd.

[0279] The conditions for the irradiation process were as follows: <Irradiation conditions> • Black panel temperature: 63℃ ·Illuminance: 100mW / cm 2 ·Battle humidity: 50%RH • Time: 20 hours

[0280] The conditions for the condensation process were as follows: <Irradiation conditions> • Black panel temperature: 30℃ ·Illuminance: 0mW / cm 2 ·Battle humidity: 98%RH • Duration: 4 hours

[0281] Using the method described above, the peel strength of the coating sheet after the weathering test of the steel structure in each example was measured. The measurement results of the peel strength after the weathering test are shown in the "Peel Strength After Weathering Test" column of Tables 1 and 2. The "Peel Strength Reduction Rate" column in Tables 1 and 2 shows the ratio of the peel strength after the weathering test to the initial peel strength. The ratio is expressed as a percentage in units of "%". In the samples with shortened drying time, the decrease in peel strength after the weathering test was effectively suppressed compared to the samples with shortened drying time.

[0282] <<2-4. Tuck>> During the manufacturing process of the steel structures in the examples and comparative examples, the tack of the rust-preventive paint or topcoat paint applied to the steel material was measured using the method described above. A tacking tester "TAC-II" manufactured by Resca Co., Ltd. was used to measure the tack. The tack measurement was performed immediately before laminating the coating sheet onto the paint film or before applying the primer paint onto the paint film. The tack measurement results are shown in the "Tack" column of Tables 1 to 3.

[0283] [Table 1]

[0284] [Table 2]

[0285] [Table 3]

[0286] In the steel structures according to Examples 1 and 2, delamination and peeling were observed when the drying time was 0 hours and 0.5 hours, respectively, but no delamination or peeling was observed when the drying time was 2 hours or more. When the drying time was 2 hours or more, the tack became 2.0 N / φ5 mm or less. In other words, in the steel structures according to Examples 1 and 2, sufficient bonding between the coating sheet and the bonding layer was achieved by drying until the tack became 2.0 N / φ5 mm or less, or by drying the coating film for 2 hours or more. It was found that a good condition could be achieved.

[0287] In Comparative Example 1, when the drying time was 4 hours or less, the primer redissolved the rust-preventive layer, causing the paints to mix and resulting in an uneven layer thickness. Consequently, the coating was defective, and peeling could not be evaluated. On the other hand, when the drying time was 24 hours, a good coating film was formed.

[0288] Based on the above, it was found that the steel structures according to Example 1 and Example 2 can be manufactured in good condition even with a shorter drying time than the steel structure of Comparative Example 1.

[0289] Furthermore, in Examples 1 and 2, when the drying time was 2 hours, the ratio of the peel strength after the weathering test to the initial peel strength was 75%. On the other hand, when the drying time was 24 hours, the peel strength after the weathering test to the initial peel strength was less than 70%. Therefore, a shorter drying time and higher tack result in the coating sheet adhering to the paint for a longer period. In other words, it can protect steel structures for a longer period. [Explanation of Symbols]

[0290] 10: Steel structure, 11: Surface, 12: Deteriorated part, 18: Rust prevention layer, 19: Topcoat layer, 20: Steel material, 21: Rust, 22: Surface preparation surface, 30: Covering sheet, 31: First surface, 32: Second surface, 33: Base material, 34: Weather-resistant layer, 35: Bonding layer, 36: Barrier layer, 37: Second bonding layer, 38: Release film, 41: Rust prevention layer, 42: First undercoat layer, 43: Second undercoat layer, 44: Intermediate coat layer, 45: Topcoat layer, 50: Coating film, 50P: Active film, 51: Rust prevention layer, 52: First undercoat layer, 53: Second undercoat layer, 54: Intermediate coat layer, 55: Topcoat layer, 100: Steel structure, T: Tack

Claims

1. A process for preparing the surface of deteriorated parts of steel structures, including steel materials, The process of applying paint to the steel material to form a coating film, A step of drying the coating film until the tack of the coating film becomes 2.0 N / φ5 mm or less, A method for repairing a steel structure, comprising the step of joining a coating sheet to the coating film using a bonding layer contained in the coating sheet.

2. The method for repairing a steel structure according to claim 1, wherein the drying step includes a step of evaluating the tack of the coating film.

3. A process for preparing the surface of deteriorated parts of steel structures, including steel materials, The process of applying paint to the steel material to form a coating film, The process of drying the aforementioned coating for two hours or more, A method for repairing a steel structure, comprising the step of joining a coating sheet to the coating film using a bonding layer contained in the coating sheet.

4. The method for repairing a steel structure according to any one of claims 1 to 3, wherein the total light transmittance of the covering sheet is 70% or more.

5. The method for repairing a steel structure according to any one of claims 1 to 3, wherein the haze transmitted through the covering sheet is 97% or less.

6. The method for repairing a steel structure according to claim 1 or 2, wherein the tack of the bonding layer is greater than the tack of the paint.

7. The method for repairing a steel structure according to any one of claims 1 to 3, wherein the bonding layer contains an acrylic adhesive.

8. The method for repairing a steel structure according to any one of claims 1 to 3, wherein the paint is a two-component curing solvent-based paint.

9. The aforementioned covering sheet contains an ultraviolet absorber, The method for repairing a steel structure according to any one of claims 1 to 3, wherein the maximum spectral transmittance of the coating sheet at a wavelength of 300 nm to 350 nm is 1% or less.

10. The method for repairing a steel structure according to any one of claims 1 to 3, wherein the paint is an epoxy resin paint.

11. The method for repairing a steel structure according to any one of claims 1 to 3, wherein the paint is a urethane resin paint or a fluororesin paint.

12. The method for repairing a steel structure according to claim 1 or 2, wherein in the drying step, the coating film is dried so that the tack of the coating film is 0.38 N / φ5 mm or more and 2.0 N / φ5 mm or less.

13. The water vapor permeability of the coating sheet under a temperature of 40°C and a humidity of 90% RH is 3.0 g / (m²). ２ A method for repairing a steel structure according to any one of claims 1 to 3, wherein the number of days is less than or equal to the number of days.

14. The method for repairing a steel structure according to any one of claims 1 to 3, wherein the oxygen permeability of the covering sheet under a temperature of 23°C and a humidity of 60% RH is 6.57 cc / (m²·day·atm) or less.

15. The process of applying paint to steel material to form a coating, A step of drying the coating film until the tack of the coating becomes 2.0 N / φ5 mm or less, A method for manufacturing a steel structure, comprising the step of joining the coating sheet to the coating film using the bonding layer contained in the coating sheet.

16. The process of applying paint to steel material to form a coating, The process of drying the aforementioned coating for two hours or more, A method for manufacturing a steel structure, comprising the step of joining the coating sheet to the coating film using the bonding layer contained in the coating sheet.

17. Steel materials, The coating film and The covering sheet and the following are included in this order: A steel structure in which the ratio of the peel strength of the coating sheet to the coating film after the weathering test to the initial peel strength of the coating sheet to the coating film is 70% or more.

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